1. PROCESS: METAL SURFACE FINISHING ’ 2. SIC CODE: 3471 3. INDUSTRY DESCFUPTION Metal finishing is a part of the plating and polishing industry classified under Standard Industrial Classification (SIC) 3471. This industry is comprised of establishments primarily engaged in all types of electroplating, plating, anodizing, coloring, and finishing of metal and formed products for the trade. Most of the work performed by this industry is done on materials owned by others. Though metal surface finishing is classified under SIC 3471, metal finishing operations are performed by many other industries included in SIC groups 34 through 39 (USEPA 1980). The metal finishing process includes some 44 unit operations and only the metal surface finishing operations that use chemical means are discussed in this report. 3.1 Company Size Distribution Since metal surface finishing operations are performed by various industries classified under many SIC codes, company size distribution data for metal surface finishing as an industry was not separately available. In 1980, there were approximately 160,000 manufacturing facilities in the U.S. which were covered by the metal finishing category (USEPA 1980). These facilities varied greatly in size, age, and number of employees. They ranged from very small independent job shops with less than ten employees, to small shops within large corporations, to large facilities employing large work forces. 3.2 Principal Producers The metal surface finishing industry is dominated by small job shops employing less than 20 employees each. There are no major producers who control a large share of the market. 3.3 Geoqraphical Distribution The geographical distribution of the metal surface finishing industry was not available due to the reasons stated above.
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1. PROCESS: METAL SURFACE FINISHING ’ 2. SIC CODE: 3471
3. INDUSTRY DESCFUPTION
Metal finishing is a par t of the plating and polishing industry classified under Standard Industrial Classification (SIC) 3471. This industry is comprised of establishments primarily engaged in all types of electroplating, plating, anodizing, coloring, and finishing of meta l and formed products for the trade. Most of t he work performed by this industry is done on mater ia ls owned by others. Though meta l surface finishing is classified under SIC 3471, meta l finishing operations a r e performed by many o ther industries included in SIC groups 34 through 39 (USEPA 1980). The metal finishing process includes some 44 unit operations and only the meta l surface finishing operat ions tha t use chemical means a re discussed in this report.
3.1 Company Size Distribution
Since metal sur face finishing operations a r e performed by various industries classified under many SIC codes, company size distribution d a t a for me ta l sur face finishing a s an industry was not separately available. In 1980, the re were approximately 160,000 manufacturing facil i t ies in the U.S. which were covered by the metal finishing category (USEPA 1980). These faci l i t ies varied great ly in size, age, and number of employees. They ranged from very small independent job shops with less than ten employees, t o small shops within large corporations, t o large faci l i t ies employing large work forces.
3.2 Principal Producers
The meta l surface finishing industry is dominated by small job shops employing less than 20 employees each. There a r e no major producers who control a large share of t he market.
3.3 Geoqraphical Distribution
The geographical distribution of t h e meta l surface finishing industry was not available due to the reasons s t a t ed above.
4. PRODUCTS AND THEIR USE
The meta l surface finishing industry deals mostly w i th the t reatment o f meta l l ic or non-metallic products manufactured by others. Each product requires a specif ic
process sequence to obtain the desired physical, chemical, or aesthetic propert ies
desired by the user. The pr incipal products of the m e t a l surface finishing industry
include:
Pr inted c i rcu i t boards
C o i l coating
Automot ive parts
K i tchen utensils
Jewelry
Mechanical (non-automotive) parts
5. RAW MATERIALS
Reagents phosphoric acid, secondary or ter t iary m e t a l phosphates, sodium
dichromate, sodium nitrate, sodium cyanide, bar ium chloride, sodium
chloride, sodium carbonate, sodium cyanate, ammonia, si l icon te t ra-
chloride, zinc oxide, chromic acid )
Accelerators quinoline, toluidine, nitrophenols, various oxidizing agents such as
Meta l surface treatment consists of various processes such as electroplating,
electroless plating, anodizing, chemical conversion coating, cleaning, etc. (USEPA 1980, BCL 1976, Schneberger 1981, Durney 1984). Since electroplat ing and meta l
surface cleaning are discussed in separate studies in this appendix, this study
considers only chemical surface treatments such as electroless plating, chemical
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7> conversion coating, etching, chemical milling, and some forms of case hardening t rea tment . Metal sur face t r ea tmen t is performed mainly t o modify the meta l sur face t o b e less reac t ive and more corrosion-resistant and is dependant on t h e type of required surface modification. All the meta l surface t r ea tmen t processes have th ree basic steps: sur face cleaning or preparation, sur face t r ea tmen t , and rinsing or post- finishing operations. The cleaning and post-finishing operations are specific t o t h e sur face t r ea tmen t method used. The following sections describe various sur face t r ea tmen t methods with t h e exception of coil coating. All chemical sur face t r ea tmen t operations are essentially ba tch operations, where the meta l object is dipped in a ba th containing various reagents to achieve the required surface modification,
6.1 Electroless Plat ing
Electroless plating allows for the deposition of meta l on an object's surface without the use o f external e lec t r ica l energy. This is achieved by a chemical reduction process which depends upon t h e ca ta ly t ic reduction of a metall ic ion in an aqueous solution. This process has found widespread use due to several advantages over conventional electroplating which include abil i ty t o produce a uniform c o a t on all a reas of t he par t regardless of its geometry without the need to supply ex terna l e lec t r ica l energy. Copper and nickel e lectrbless plating a r e the most common.
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The basic ingredients of e lectroless plating solutions a r e a source of me ta l ions (generally copper or nickel), a complexing agent t o maintain ions in solution a t t he operating pH value, a compat ible reducing agent, a mater ia l t o adjust t h e pH of t h e bath, and s tabi l izers , wet te rs , stress relievers, etc. Table 6-1 lists the bath const i tuents f o r copper and nickel e lectroless plating operations.
The electroless plating operation consists of cleaning the object surface, immersing it in a ba th containing the previously described const i tuents for a specif ic period of t ime, and then rinsing the object ( a f t e r removal f rom the bath) t o remove process solutions adhering to t h e surface.
Plating bath solutions las t only a f e w hours because ca ta ly t ic par t ic les precipi ta te in ly increased by periodic fi l tration, and by the addition the bath. The bath life
.-.I s usua
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Table 6-1 Bath Constituents for Capper and Nickel Electroless Pla t inq
~~
Funct ion Copper Plat inq Operation Nickel P lat inq Operat ion
Rochelle s a l t (sodium potassium tartarate, eth ylenedi aminetetracetic acid (EDTA), sodium salts of EDTA, n i t r i lo t r iace t ic acid, qluconic acid, gluconates, tr iethanol amine, n-hydroxy ethylene diamine tetracetate (20-50 q/l).
Lact ic acid, dicarhoxylates
Formaldehyde, paraformaldehyde, t ri oxene, dimethylhydantoin, sodium and potassium borohydride.
Sodium hyposphosphi t e
Sodium or potassium hydroxide Sodi urn or potassium hydroxi de
Source: Development Document for Eff luent L im i ta t i on Guidelines (USEPA 1980).
-) of stabilizers. The bath is eventually dumped thereby generat ing a waste s t ream. Other waste s t reams a r e generated by rinsing operations and periodic cleaning o f t he process equipment. Other e lectroless plating operations, such as vapor deposition, a r e purely physical operations and are not considered in this report .
6.2 Chemical Conversion Coat ing
This operation includes phosphating, chromating, meta l coloring, and passivating. The
coat ing deposited on metal objects is for decorat ive or corrosion protect ion purposes, and in some instances t o prepare the surface for painting. The mode of operation and waste generation a re similar t o the electroless plating operat ion described in Section
6.1. The following sect ions discuss the four different chemical conversion coating methods l isted above.
6.2.1 Phosphating
Phosphate coatings a re formed on the surfaces of iron, s teel , galvanized s tee l ,
aluminum, and electrodeposited zinc and cadmium t o promote adhesion of organic coatings, to re ta rd interfacial corrosion, to re ta in and enhance the performance of corrosion resis tant oils, and to assist in cold deformation processes. Small par t s a r e coated in barrels immersed in the phosphating solution and’ l a rge pa r t s a re spray coa ted or continuously passed through the phosphating solution. The object to b e coated may be dipped successively in a ser ies o f processing tanks.
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The phosphating solution consists of a phosphoric acid solution of meta l dihydrogen phosphate. The coating t ime and tempera ture depends on the type o f metal t o be coa ted and whether a spray or immersion coat ing scheme is used. Sometimes acce lera tors ( to improve quality), s tabi l izers ( to prolong bath life) and oxidizing agents ( t o control the coat ing ra te ) a r e added to the phosphating solution.
There a r e cer ta in parameters , such a s the ra t io of free t o combined phosphoric acid, to ta l acid, metal-ion concentrat ion, acce le ra tor concentration, and the process tempera ture t h a t must be controlled to achieve a suitable coat ing and maintain t h e
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integr i ty of the bath. The coated object, af ter phosphating, may be given a
conditioning rinse w i th di lute chromic and/or chromic-phosphoric acid for surfaces to
be protected against corrosion, or an alkaline rust- inhibi t ing t reatment for objects t o
be cold-deformed. Concerns about the environmental e f fects o f chrome have led t o
the development of chrome-free rinses. Though these are less ef fect ive than the i r
chrome-containing counterparts, they are suitable for applications where corrosion is
not a major concern.
6.2.2 Chromating
Chromate coatings are most frequently applied on zinc, cadmium, aluminum,
magnesium, copper, brass, bronze, and silver to minimize rust format ion and t o
guarantee paint adhesion. Chromate-type conversion coatings are produced pr imar i ly
by a simple immersion process although a spray or brush treatment can be used.
The chromatin9 solution consists o f chromic acid, one or two mineral acids such as
sulfuric or nit r ic, and o f ten some act ivat ing compounds. Chromate conversion
coatings are formed because the meta l surface dissolves to a small extent, Causing a
p H rise a t the surface-l iquid interface. This results in the precipi tat ion of a thin
complex chromium meta l gel on the surface, composed of hexavalent and t r iva lent
chromium and the coated m e t a l i tself . This gel is normally soft when formed and must
be handled carefully. A f t e r drying, the coating becomes hard and relat ively abrasion-
resistant.
The thickness and color o f the chromate coating depends on the solution composition,
temperature, pH, and the length o f treatment. The coated object i s usually rinsed
w i t h cold water containing sodium hydroxide or sodium carbonate to provide a clear
noniridescent coating. This is fo l lowed by a warm water rinse to prevent the removal
o f the coating.
6.2.3 Meta l Coloring
Whi le coloring o f steel, copper, aluminum, and their alloys i s done pr imar i ly for
aesthetic purposes, this surface t reatment o f ten imparts other favorable propert ies
such as improved corrosion resistance and be t te r abrasion and wear characteristics.
The coating operation i s pr imar i ly o f the immersion type.
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-3 Many formulations a r e available for the coloring of meta ls and most of t hem a r e proprietary. The major coloring process for steel uses a t r ea tmen t solution of sodium hydroxide and sodium n i t r a t e in water. The processing tempera ture may vary from 275-320OF, and t h e immersion t ime may vary f rom 5 t o 30 minutes. The coating color and character is t ics are largely a function of t he alloy being t reated, sur face character is t ics , concentrat ion of the bath, t empera ture , and immersion t ime.
6.2.4 Passivation
Passivation re fers to forming a protect ive fi lm on metal , particularly stainless s t ee l and copper, by immersion in an acid solution. Stainless s tee l is passivated t o dissolve embedded iron par t ic les and t o form a thin oxide fi lm on its surface. A typical
t r ea tmen t solution for stainless steel is ni t r ic acid or nitric acid with sodium dichromate. Copper is passivated using a solution of ammonium sul fa te and copper sulfate.
6.3 Chemical Etchinq
Chemical etcMng is used t o produce specific design configurations and tolerances on metall ic or metal-clad plast ic (printed circuit boards) by controlled dissolution of t h e meta l with chemical e tchants . Typical e tching solutions are fe r r ic chloride, ni t r ic acid, ammonium persulfate, chromic acid, cupric chloride, hydrochloric acid, etc. "Bright dipping" is a special form of chemical e tching used t o remove oxide layers f rom ferrous and non-ferrous materials.
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6.4 Cyaniding
Cyaniding is a type of case hardening t h a t produces a hard surface on a meta l whose core remains relatively sof t . The product is a hard, wear-resistant surface backed by
a strong, ductile, and tough core. Carbon and alloy s t ee l s a r e usually immersed in the
cyaniding bath fo r a specif ic period of t i m e t o achieve the required degree of su r face hardening.
The most common cyaniding solution consists of 30 percent sodium cyanide, 40 percent sodium carbonate , and 30 percent sodium chloride. Baths containing 97, 75, and 45
percent sodium cyanide a r e also used. Oxygen f rom the a i r oxidizes the sodium
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cyanide to sodium cyana te which, a t high temperatures , decomposes to form nascent carbon and nitrogen. The carbon and nitrogen a re absorbed by the s teel , which increases surface hardness. The processing temperatures may vary from 1200-135OOF
fo r low penetrat ion t o 1650-1725OF for high penetration. A combination t r ea tmen t using high tempera ture immersion followed by low tempera ture immersion is also used.
The depth of surface tha t is hardened is controlled by the tempera ture and the cyanide content . As drag-out and carbon depletion occur, special s a l t compositions a r e added to replenish and regenera te the bath. At the end of the t rea tment , the objects are immersed in a water or oil bath, where quenching and rinsing is accomplished simultaneously. The quench water is potentially hazardous and is t rea ted for cyanide destruct ion followed by clarification prior t o discharge. The quench oil is also
potentially hazardous and is disposed of by incineration.
7. WASTE DESCRIPTiON
The primary wastes associated with metal surface finishing, along with the i r process sources, are listed in Table 7-1. The wastes produced in meta l surface finishing operations come mainly f rom two sources: dumping of process tanks, and rinse waters used to wash off process solutions adhering to the product surface or entrapped in t h e crevices due to the shape of the product piece (Durney 1984, AESI 1981, CP Staf f 1984). The process solutions a r e periodically fi l tered to remove precipi ta ted meta ls and a r e reused. These f i l tered solids a re mixed with solids.removed from the rinse waters and a r e e i ther landfilled or sold for meta l reclamation.
Additional was te is generated a s a result of process solution filtering.
Other wastestreams include spills and leaks plus stripping wastes.
Spent Bath Solution
The activity of t he plating solution decreases with t ime due t o the precipi ta t ion of sal ts and depletion o f consti tuents. Af te r 3-6 regeneration cycles, the ba th is
eventually discharged*. This waste s t ream usually contains cyanides or meta l l ic
~ ~~~
*National Association of Metal Finishers 1985: Personal communication.
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Table 7-1 Meta l Surface Finishing Wastes
2. Waste rinse water
W m
Waste No. I lescr ip t ion
RCRA Process Origin Composition Code
1. Spent bath solution Dumping of the process cyanides, cyanide com- F011 solutions a f te r depletion plexes, hexavalent or loss o f act iv i ty. chrome, copper, nickel,
zinc, cadmium, and other metals and their salts in water
\D
3. F i l t e r waste
4. Spills and leaks
5. Stripping waste
Rinsing treated objects, equipment cleaning, solution quenching o f case hardened steel.
same as spent ba th
F i l t ra t ion of process Complexes o f various FOlO solution, spent baths, metals, cyanides, etc. F012 and treated waste rinse water.
Overf lows and leaks f r o m various process equipment
same as (1)
Removal of coatings not available f rom improperly treated objects.
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complexes. I n the recent past, this stream was treated together w i th the rinse water
stream. However, the need for obtaining the necessary permi ts and also the perceived
regulatory compliance d i f f icu l t ies have discouraged treatment o f spent baths*. This
stream is of ten sent of f -s i te for disposal.
Waste Rinse Water
Rinse water i s used to wash o f f process solutions adhering t o the product surface or entrapped in i t s crevices due to i t s geometr ical shape. The rinse water stream is
usually discharged to municipal t reatment faci l i t ies w i th or without any treatment,
depending on i t s composition. The treatment procedure includes oxidative destruction
of cyanides reduction o f chromates, neutralization, and solids removal.
F i l t e r Waste.
The f i l t ra t ion step in the regeneration of p lat ing solut ion and the solids removal in
rinse water t reatment each generate a solid waste. These solids contain oxides or complexes of metals and are either landf i l led or sent of f -s i te fo r meta l reclamation.
S p i l l s and Leaks
The overf low and leaks f r o m various process equipment are usually mixed w i t h the
rinse water stream and disposed of as explained above.
Strippinq Waste
Before coating an object, the previous coatings on it are removed by a str ip ing
operation. This i s also done t o remove coatings f r o m an improperly coated object. In
smal l job shops, the same stripping solution could be used fo r removing d i f ferent types
o f coating. The disposal o f the spent bath f r o m such operation is similar t o tha t o f the
spent baths discussed earlier. The rinse waters are usually discharged t o municipal
t reatment faci l i t ies wi th or without treatment. The untreated streams may contain
various cyanides and cyanide complexes, hexavalent chrome, copper, nickel, zinc,
* Westinghouse Elect r ic Corporation, 1985: Personal communication
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3 cadmium and other metals. The t r ea tmen t includes oxidative destruction of cyanides, The t r ea tmen t sludge is
Spills and overflows t h a t occur can be mixed and t rea ted reduction of chromates, neutralization, and solids removal. expected to be landfilled. with o ther liquid wastes and t rea ted as discussed.
8. WASTE GENERATION RATES
Since metal finishing operations a re of ten performed along with electroplating and o ther operations, the waste generation r a t e s specifically a t t r ibutable to me ta l finishing are difficult t o determine. N o waste generat ion d a t a were in evidence a t t h e t ime of the final document preparation. While no specific waste generation r a t e s were reported, f ract ional r a t e s were es t imated by project s ta f f based on the available
information and engineering judgements. These values a r e shown in Table 9-1.
9. WASTE REDUCTION THROUGH SOURCE CONTROL
9.1 Description of Techniques
The list of individual waste s t r eams and sources and their corresponding source reduction methods is presented in Table 9-1. The following sect ions discuss the various waste reduction methods based on a l i t e ra ture survey and industry contacts .
In addition to the waste reduction measures classified a s being process changes or
mater ia l /product substi tutions, a variety of waste reducing measures labeled as "good operat ing practices" has also been included. Good operating pract ices a re defined a s being procedural or insti tutional policies which result in a reduction of waste. The following i tems highlight the scope of good operat ing practice:
o Waste s t r eam segregation o Personnel pract ices
- management init iatives - employee training
o Procedural measures - documentation
- material handling and s torage - - scheduling
mater ia l tracking and inventory control
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o Loss prevention practices
- spi l l prevention
- preventive maintenance
- emergency preparedness
For each waste stream, good operating pract ice applies whether i t is l is ted or not.
Separate listings have been provided whenever case studies were identified.
9.1.1 Spent Bath Solutions
Most o f the meta l surface f inishing operations are performed by immersing an object
into tanks containing specif ic reagents. Due t o the precipi tat ion o f salts and deplet ion
of constituents, the bath becomes inef fect ive and must be regenerated or discarded
when necessary. This waste, containing cyanide, cyanide complexes of metal, and
other metal l ic complexes, i s o f ten sent t o a t reater for disposal. The fol lowing
methods could reduce this waste stream:
o Extending bath l i fe.
During the surface treatment operation, many insoluble salts (such as
ferr ic phosphate in the case o f ferrous meta l phosphating) precipi tate out
o f solut ion and thereby decrease i t s effectiveness. In addition, the
depletion o f meta l in the solution causes the ac t iv i t y o f the bath t o
decrease. The bath life, i f prolonged, can contr ibute toward waste
reduction since the frequency o f process solution dumping decreases. The
bath l i f e can be increased by periodic or continuous f i l ter ing o f the bath,
regeneration o f the spent bath solution, and preventive measures against
bath contamination. As the insoluble meta l l ic salts precipi tate onto the
cooling/heating coi ls and the object, the effectiveness of the bath goes
down. By periodical ly f i l te r ing the process solution, i t s act iv i ty can be
maintained (Durney 1984, Saubestre 1957). This i s already pract iced a t
many m e t a l finishing operations, especially those w i t h chemical conversion
coatings.
i iemoval o f the soluble salts formed during the t reatment process can also
extend bath l i fe. The soluble meta l l ic salts that fo rm during the t reatment
process accumulate in the bath and reduce i t s effectiveness. These salts 1
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can somet imes be removed by temporarily lowering t h e ba th t empera tu re so as t o form solid crystals. In the case of e lectroless nickel plating, t h e sodium su l f a t e t ha t forms can be crystall ized by lowering the bath
tempera ture t o 41-500F (Durney 1984). The crystals can then be removed
by fi l tration.
Another process, patented by the U.S. Army, involves the removal of
sodium carbonate f rom sodium cyanide-based plating ba ths by cooling. Dry ice is used t o cool t he plating bath, thereby causing the precipitation of t he carbonates. The plating solution, free of carbonates, can then be reused.
So fa r , th i s method has not found widespread use (Arienti 1985, Versar 1985).
Use of an e lec t ro ly t ic diaphragm cel l for regenerating spent chromic acid used in e tching operations has been reported (AESI 1981). The process uses electrolyt ic diaphragm cel l t o oxidize tr ivalent chromium t o hexavalent chromium and remove contaminants. The quality of the regenerated e t chan t was reported t o be equal t o or be t t e r than fresh etchant . This process, which was s t i l l in the developmental s tage, would have a g rea t potent ia l for reducing spent chromic acid waste. In one such application, extensively tes ted a t the U.S. Bureau of Mines in Rolla, Mo., copper e tching solution was regenerated and metall ic copper recovered a t t h e same time. Recovery was accomplished by depositing t h e copper onto t h e cathode of t he e lec t ro ly t ic diaphragm cell (Basta 1983).
Other measures tha t can extend bath life a r e t o use au tomat ic control systems, maintain a l l rack and barrel systems, and prac t ice good house- keeping a t all t imes. Automatic control devices can be used t o maintain
the concentrat ion by conductivity measurement. A significant change in conductivity would in i t ia te pumping of f resh concent ra te into the tank. This type of au tomat i c control is used by large faci l i t ies especially f o r ch romate conversion coat ing (Durney 1984). If t he racks or barrels (used for t ransferr ing objects t o be coated) do not have proper protect ive coatings, t he bath could become contaminated. The process solution can a t t ack the weak spots in the racks or barrels, causing the formation of metal l ic s a l t s in the bath and thereby lower its activity. Fluorocarbon
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coat ings applied to the racks or barrels have been found t o be e f f ec t ive in 1 minimizing such contamination (Lane 1985). Such a coat ing will also be
helpful in lowering dragout since less bath solution t h a t remains in the corroded crevices on the racks or barrels. Special measures tha t cons t i tu te good operating pract ices a re discussed a t t he end of this section.
o Metal/acid recovery from spent bath solutions. By using electrolysis on the spent bath solutions, useful meta ls can be recovered and a t the same t ime the hazardous na ture of t he spent ba th can be reduced (Lewis 1980, Campbell and Glenn 1982). This method was
implemented in one facil i ty by insertion of e lectrodes direct ly into the cyanide destruction tank*. However, electrolysis is used only t o a l imited ex ten t by the industry (USEPA 1982).
In addition t o recovering metals f rom the spent bath, spent acid can also be recovered and recycled by means of ion-exchange (Basta 19831. Eco-Tec Ltd., in Ontario, Canada, markets an acid purification sys tem t h a t uses a proprietary resin tha t recovers mineral acids. The meta ls are recovered in a concentrated (but s t i l l dissolved) form. The concent ra ted me ta l s can than be recovered by electrolyt ic means. This process is used by Modine Manufacturing, in Trenton, Mo., t o t r e a t copper-contaminated sulfuric acid/hydrogen peroxide solution which was used t o brighten brass (Basta 1983). Sodium phosphate salts, formed in nickel/copper e lectroless plating, can be converted into useful hypophosphite salts by using ion exchange resins act ivated with hypophosphorous acid. The use of ion exchange resins for regeneration, however, suffers f rom the disadvantage of generat ing
additional wastes such a s spent resins and resin regenera tion solutions.
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Another nonelectrolytic means of meta l reclamation, s t i l l in developmental s tages , is the use of bac ter ia (Basta 1983). Here, t h e microbes form complexes with the metals in solution, creat ing a biomass. The biomass can then be burned t o recover e lementa l metal . Laboratory s tudies in this a r e a a r e in progress a t Polbac Corp. (Allentown, Pa.) and t h e O'Kelly Companies (Tulsa, Ok.).
* National Association of Metal Finishers 1985: Personal communication B6-14
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Another new trend is the use o f so-called l iqu id membranes. These
membranes are composed o f polymeric mater ia ls loaded w i t h an ion-
carry ing solut ion (Basta 1983). L iquid membranes were used a t Bend
Research Inc., in Bend, Ore., t o remove chromium f r o m rinse waters and
spent baths. Here, chromium in the form of dichromate is drawn across
the membrane, forming a ter t iary amine meta l complex. This complex i s
then broken down on the other side o f the membrane w i t h sodium hydroxide
solution. Similar experiments are in progress a t the Warren Springs
Laboratory in Stevenage, England, for t reat ing wastes f r o m pr inted c i rcu i t
board manufacturing.
o Spray/brush methods instead o f immersion methods.
The use o f spray/brush methods, which use reagents in a more e f f i c ien t manner, w i l l reduce the to ta l amount o f spent reagents generated. How-
ever, spray methods are useful only in continuous applications and when the
objects are f l a t or geometrical ly simple. Brush application methods are
also useful only where the geometry o f the object and/or the nature o f t h e
operation permi ts it.
o Use o f thinner foi ls in pr inted c i rcu i t boards manufacture.
Pr in ted c i rcu i t boards are made by the control led dissolution o f the m e t a l
f o i l present on a plast ic substrate in an etching solution. By using a thinner
meta l f o i l on the plast ic board, lower amounts o f etching solut ion are
needed and more di lute solutions can be used. This w i l l resul t in less spent
bath wastes. Other techniques al lowing for reduction in etching solut ion
use are described in the-study o f pr inted c i rcu i t boards manufacture ( B l l ) .
o Al ternat ives to conventional meta l surface treatment techniques.
In cyaniding, l iquid cyanide salts are used to generate nascent carbon and
ni t rogen tha t dif fuse in to the meta l surface, causing it t o harden. The
same result can be achieved when carbon and steel are exposed to ammonia
gas. Ammonia decomposes a t about 1550OF t o produce nascent nitrogen.
Combined w i t h carbon, the gas w i l l di f fuse in to the meta l surface. The use
of gas phase carbonitr iding alleviates the need fo r a cyanide solut ion bath.
I n addition, the quench-rinsing sequence present in the l iquid phase
carboni t r id ing (cyaniding) process would also be avoided. Thus, the waste
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generated by spent bath solutions can be eliminated totally. Zyaniding, however, does have several advantages over gas carboni triding (Schneberger 1981). These include more flexible opera tion i l lustrated b y
the ability to simultaneously t r ea t many small batches which require different cycle times, and a higher heating rate . This is important for cases where the t ime needed fo r the object t o reach the conditioning temperature may be a large f rac t ion of the to ta l cycle time.
Vacuum evaporation methods for coating nickel, aluminum, and o ther metals have been developed. Here, meta ls a r e evaporated a t low pressure using an electron beam and the vapor condenses, a s a coating, onto the substrate. This method could be a viable a l te rna t ive to e lectroless nickel
plating, which generates spent bath wastes. However, the vacuum evaporation method has several disadvantages, e.g., it requires relatively expensive equipment which becomes effective only when a large number of substrates a re to be coated, and the uniformity of coating thickness is
generally very difficult to control.
Chromium and cadmium can be ,deposited on s tee l using ion plating methods instead of electrodeposition. Ion plating uses high-energy ions tha t bombard the depositing meta l which evapora tes and then condenses on the substrate. In the U.S., this method is used only when other techniques a re found inadequate. However, ion plating is in wide use in Japan where it successfully competes with electrodeposit ion (Durney 1984).
Chemical vapor deposition (where a chemical reaction decomposes the reac tan t gases t o produce the desired coat ing mater ia l which then condenses on the substrate) can be used for almost any coating operation (Durney 1984). However, its use has been l imited to the semiconductor industry, and commercial systems for o ther applications are not available a t the present time.
Ion beam processing techniques, s t i l l in t h e development s tage, will be an excellent a l ternat ive to case-hardening t r ea tmen t s (Anon 1984). Here, a high energy ion beam is used to harden the sur face by implanting the ions in the material . 1
56-16
1) o Use of less tox ic solutions.
Whenever possible, the use of less tox ic solutions for m e t a l finishing w i l l
lower the hazard o f spent solutions. In the case of electroless copper
plating, water soluble cyanide compounds of many metals are added t o
el iminate or minimize the internal stress of the deposit. It was found t h a t
polysiloxanes, such as General E lect r ic si l icon f lu id SF-96, are also
e f fec t i ve stress rel ievers (Durney 1984). By substi tut ing cyanides w i t h
polysiloxanes, the hazardous nature of the spent ba th solution can be
reduced, Use of t r ivalent chrome instead o f hexavalent chrome in
chromate conversion coating can el iminate the tox ic i ty o f the spent
electroplat ing baths. Though some manufacturers use t r iva lent chrome+,
i t s use i s not growing rapidly because the qual i ty o f t r iva lent chromium
coatings i s not as good as tha t o f hexavalent coatings in many
applications.+ Currently, there were a t least f i ve companies that o f f e r
t r iva lent systems (Chementator 1982). Trivalent chromium baths can also
use lower meta l concentrations. One such solution, developed by
W. Canning Materials Ltd. in Birmingham, England, uses only 3.5 gms/ l i ter
of t o t a l chromium compared t o the level o f 130 gms/ l i te rs used in
tradi t ional hexavalent baths.
o More di lute process solutions.
The use o f d i lute bath solutions, whenever possible, would also reduce the
hazardous nature of the dumped bath. In the case o f cyaniding, a typ ica l
bath solution composition i s 30 percent sodium cyanide, though some
fac i l i t ies use 45, 7 5 , and 92 percent solutions. By using a 30 percent
solution instead of a solution o f higher concentration, substantial reduct ion
in the cyanide content o f the spent bath solut ion can be achieved. In
electroless copper plat ing for pr inted c i rcu i t board manufacture, d i lute
solutions have been tr ied successfully by many manufacturers (USEP4
1981). The use of d i lute bath solut ion could also lower subsequent rinse
water requirements and meta l dragout in to rinsewater.
* Nationa! Association o f fvletai Finishers 1985: Personal communication. J
B 6 - 1 7
I
o Bet ter operating practices.
By frequent monitoring of the bath act iv i ty and regular replenishment o f
reagents or stabilizers, bath l i fe can be prolonged (Durney 1984). These
reagents or stabilizers di f fer f rom process to process. Stabilizers such as
2-mercaptobenzothiozole and methanol are found ef fect ive in electroless
copper plat ing used for manufacturing pr inted c i rcu i t boards. The addi t ion
o f stabilizers can sometimes decrease the deposition rate, but can s t i l l be
economical in the long run.
Good control o f the bath temperature i s important f r o m the viewpoint o f
performance predictabi l i ty and i s another method o f prolonging ba th l i fe.
Many o f the surface treatment operations use tanks w i t h immersed
cooling/heating coils. As the salts precipi tate and f o r m scales on the coils,
the heat transfer i s impeded and temperature contro l becomes increasingly
di f f icul t . The heat transfer ef f ic iency can be maintained by per iodic
cleaning o f the coi ls or by using jacketed tanks instead o f coils.
Proper storage o f the process solutions can also reduce waste generation.
Usually, the process solutions are stored as a two-part solution and are 1 mixed when a batch i s needed. Prolonged storage o f these solutions may
al low some chemical reactions to occur that could generate contaminants
that reduce bath l i fe. In electroless copper plating, i f formaldehyde (using
as a reducing agent) is stored w i t h a hydroxide, the hydroxide can cause the
formaldehyde to breakdown in to formic acid and methy l alcohol. Thus, i t
i s Setter to only store non-reactive mixtures o f mater ia ls or t o store each
i t e m separately.
9.1.2 Waste Rinse Water
A t the end o f surface treatment, objects are rinsed w i th water, alkali, or acid t o
remove reagents adhering to the surface or trapped in the crevices of the object. This
rinsing may be repeated several times, and the rinse water represents about 90 percent
66-18
3 of t h e to ta l waste volume gerera ted (AESI 1981). This s t ream, containing cyanides and
cyanide complexes along with o ther meta l complexes, is t r ea t ed for cyanide destruct ion and discharged t o the sewer. The following source control methods a r e suggested:
o Reduction of drag-out. In an immersion-type t r ea tmen t process, small objects a r e placed inside barrels and bigger objects are supported on racks for immersion into t h e bath. When the object is removed from the bath, the rack or barrel (and object) car ry some reagents with it, called "drag-out". Methods tha t can
be used to reduce drag-out and subsequently lower rinse water requirements are: proper racking o f t he parts; keeping the racks free of meta l buildup and corrosion; increasing drainage t ime above the process tank; using s ta t ionary recovery rinses by installing save rinse or drip rinse
tanks; using air blowoff or tumbling t o ensure drainage; and using drainage agents (Cheremisinoff, Peina, and Ciancia 1976, AESI 1981, and Cook et. al. 1984).
1 o Effect ive rinsing methods. By using an e f f icent rinsing sequence, t he quantity of rinse water required can be reduced substantially. Rinsing efficiency can be improved by using properly designed rinse tanks, using a i r agi ta t ion in the rinse tanks, using fog sprays, using au tomat i c valves tha t control flow r a t e s based on t h e movement of p a r t s through the processing line, and by using counter- cur ren t rinsing (Cheremisinoff, Peina, and Ciancia 1976, AESI 1981, and USC 1983).
An es t imated 90 percent reduction in rinse water can be achieved by using a countercurrent rinse instead of a single running r inse (AESI 1981).
Converting t o a countercur ren t rinse requires only the addition of one or more tanks, appropriate plumbing, and an a i r agi ta t ion system. Because of space l imitat ions or t h e use of preprogrammed hoist lines, installation of an additional rinse tank may not be possible a t many job shops. However, many faci l i t ies have reported substantial savings by converting t o countercurrent rinsing.
56-19
The use of f low control valves can reduce rinse water use by 50 percent
w i t h min imal capi ta l costs (AESI 1981). I n many instances, excess water i s
used indiscriminately to ensure to ta l rinse to p ro tec t product quality.
Though many faci l i t ies have instal led f low control valves, concerns about
reduced product qual i ty have contr ibuted to opposition t o such measures
(AESI 1981).
Fog sprays, though eff icient, are not suitable for a l l applications. In
instances where the coating has l i t t l e strength in i t ia l ly (as in the case o f
chromate coatings), fog sprays are generally not used. Use o f a i r agi tat ion
in the rinse tanks promotes turbulence in the tank which increases the
r insing efficiency. The use o f a i r agi tat ion in tanks is fa i r ly widespread
(AESI 1981).
o Use of immiscible rinses.
The use o f non-aqueous immiscible solvent fo r r insing would al low the
rinsed solution t o either sink or rise during decantation, and the solut ion
could then be returned t o the surface t reatment bath for reuse without any
pretreatment. The rinsing solvent could also be recycled. This process, i f
feasible, could reduce or el iminate rinse water wastes. Tests w i t h f ive
solvents fo r use in the chromatin9 process were conducted a t the Uni ted
Technologies Research Center (AESI 1981). A major disadvantage of this
method would be the potent ia l f o r increased a i r emissions and the need t o
dispose of spent solvent.
o The use of no-rinse coating processes.
As the name suggests, no-rinse coatings do not require rinsing af ter a
coat ing is formed and dried, as there are no residuals l e f t to in ter fere w i t h
the subsequent treatment. Recent developments in chromate conversion
coat ing for the c o i l coating industry have resulted in a solution that can be
applied to steel, galvanized steel, or aluminum, wi thout the need for any
subsequent r insing (USEPA 1982). A f t e r the coat ing is formed, it is dr ied
in a i r a t about 15OoF. This no-rinse process, though used by only a few c o i l
coating faci l i t ies, can be used for other coating applications (USEPA 1982).
06 - 20
3 The no-rinse process does have some disadvantages. These are: the
inherent high speed of operation requires very e f f i c i e n t control; exist ing
fac i l i t ies are d i f f i cu l t and expensive t o adapt t o no-rinse coat ing
operations; and the no-rinse conversion coatings are no t FDA approved f o r
food grade coatings.
o Reuse/recycle of rinse water.
A l i terature review on the reuse and recycle o f process water in the meta l
finishing industry was conducted (Mathews 1980). The fol lowing paragraphs
deal w i t h some of the reuse/recycle options tha t are already in use or were
suggested f o r use.
In the chromate process, the f i r s t rinse (high in chromic acid), can be
recycled to the chromating tank (UNECE 1982). The last rinse can be
regenerated using ion-exchange resins and can then b e recycled t o the
rinsing process. Or, by sending the rinse water t o an evaporator, the
concentrate f r o m the evaporator can be recycled t o the coating bath, and
the overhead f r o m the evaporator can be condensed and used fo r r insing
(AESI 1981, Basta 1984). This scheme ( i l lustrated in F igure 9-1) can reduce
rinse wat& requirements drastically. The method requires suf f ic ient water
t o be evaporated and recycled t o satisfy r insing requirements. The
economics o f such systems has been discussed in deta i l elsewhere (AESI 1981). Case studies o f fac i l i t ies using evaporators have also been reported
(Lewis 1980). The use of atmospheric evaporators, while decreasing energy
requirements, requires signif icantly more f loor space than conventional
evaporators. Such systems are in use a t some fac i l i t ies (Campbell and
Glenn 1982).
Concentrat ion o f rinse water for recycle t o p la t ing baths or fo r reuse can
be achieved using ion exchange resins. A reciprocat ing f l o w ion exchanger
fo r drag-out recovery f r o m chromium, copper, and mixed coat ing processes
is in current usage. The use of similar ion exchange columns for rinse
water t reatment and reuse is expected t o have great potent ia l in the
future. The use of ion exchange columns does have soTe disadvantages.
These are: ion exchange i s more expensive than conventional chemical
8 6 - 2 1
MAKE UP - SOLUTIONS
PRODUCT AND ORAG-OUT
I L-d
RINSE TANK
i _- - - -
FIN ISHEO PRODUCT -- . ___ __I
--
EVAPORATOR Y CONCENTRATED TREAT I N 6 SOLUTION ------
4 MAKE UP RINSE WATER
Figure 9- i Closed Loop Evaporation Systen for Metal Surface Treatrent Maste Reduction
t rea tment ; regenerat ion s teps genera te the i r own wastes; and the process is only favorable for s t r eams with a low concentrat ion of contaminants (up
t o approximately 250 ppm).
Reverse osmosis for concentrat ing rinse waters has found limited use. Here, water is preferentially forced through the pores of a semi-permeable membrane and two s t reams a r e generated: a concent ra ted sa l t solution tha t can be sen t to t h e bath, and a pure wa te r s t r eam tha t can be used for rinsing. Some of the l imitations confronting t h e process a re t h a t t h e membranes opera te in the high pH range only (pre t rea tment to assure high pH is necessary); t h e reliability or durability of the membranes under variable conditions charac te r i s t ic of mixed wastewater is questionable;
supplemental evaporation ( to boost concentration) may be necessary before the sal t solution can be recycled to the coat ing process; and the process is economical only for processes with high drag-out r a t e s (something tha t can be controlled by good operating practices). Cellulose a c e t a t e membranes a r e used by some nickel coat ing facil i t ies. Other potential membrane applications include copper, zinc coating, and chromating operations.
The electrodialysis process uses a l ternately placed anion and cat ion permeable membranes and separa tes the rinse waters into a dilute s t r eam t h a t can be used fo r rinsing and into a concent ra ted s t r eam tha t can be recycled t o the coat ing operation. The process is continuous and the major operating cost is for electricity. Currently, some nickel, zinc, and chroinating faci l i t ies use this process.
o Replacing hexavalent chromium with tr ivalent chromium. In chromate conversion coatings, hexavalent chromium can be replaced by t r ivalent chromium, which reduces the hazardous nature of rinse waters. This method is discussed in more de ta i l in Section 9.1.1.
o Replace cyaniding by gas carbonitriding. As explained in Section 9.1.1, cyaniding requires a quench-rinse operation t o wash cyanides present on the objects. The use of gas carbonitriding eliminates the need for this rinsing operation tha t genera tes a hazardous
waste s t ream.
5 6 - 2 3
0
I
Use of s t i l l rinsing. The work piece can be immersed in a s t i l l rinse tank following the meta l finishing bath. The still rinse tank has no inflow or outflow of rinse water , and the finishing bath consti tuents build up in it. When t h e rinse water in the s t i l l rinse tank becomes concentrated enough, it can be used to replenish the finishing ba th solution. The use of s t i l l rinsing c a n c u t down t h e quantity of rinse water required. This process, when used for init ial rinsing, c a n faci l i ta te meta l recovery f rom t h e rinse water. Still rinsing is usually followed by a spray or countercurrent rinse to ensure the comple te removal of contaminants.
o Metal reclamation from rinse water wastes.
By using electrolyt ic or non-electrolytic methods, as explained in Sect ion 9.1.1, meta ls present in the rinse waters can be recovered. This reduces the hazardous nature of this stream.
o Changing rinse composition. Changing t h e rinse composition t o reduce its hazardous nature should b e a t t empted whenever possible, In a zinc-based phosphating bath, t he final 1 rinsing of t h e object is usually done with dilute chromic acid. Environ- mental concerns about chrome caused several facil i t ies t o develop and use chrome-free rinses, even though these rinses were not as e f f ec t ive a s t h e chrome-containing rinses (Schneberger 1981).
o Minimizing process water use. By reusing rinse water effluents from cer ta in operations in other operations with lower rinse water quality requirements, overall aqueous wastes can be minimized. The use of water f rom fume scrubbers h a s been
shown t o b e pract ical fo r rinsing in cer ta in cases (Cheremisinoff, Peina, and Ciancia 1976). Used cooling water or s t e a m condensate might a lso b e used f o r rinsing if technically permissible and economically justified.
o Bet te r operating practices. A typical m e t a l finishing facility has various coating operations being performed a t t h e same time, and mixing of various rinse s t r e a m s is not
86-24
uncommon. By segregating various rinses, the i r reuse or recycle can be
promoted. Meta l reclamat ion by electrolysis f r o m these various streams i s
easier i f they are not mixed together. In the recent past, rinse waters and
spent baths were mixed and treated together. Segregating spent b a t h
wastes f r o m rinse water wastes i s quite common a t present.
9.1.3 Solid Wastes
Solid wastes are generated during the f i l t ra t ion o f the ba th t o remove prec ip i ta ted
meta l l ic salts, and by the clari f icat ion, dewatering, and f i l ter ing operations per formed
during waste treatment. These sol id wastes are usually disposed o f by landf i l l ing or are sent to an outside reclaimer. The fol lowing source reduct ion techniques are
considered:
o Meta l reclamat ion f r o m the solid waste.
It was reported by L isant i and Helwick (AESI 1981) t h a t a cer ta in fac i l i t y
hauled solids to another plant wi th in i t s corporation fo r meta l reclamation.
Depending on waste volume, such recovery can be an uneconomical
proposit ion in terms of capi ta l costs. Individually, the quanti t ies generated
might no t be large enough t o just i fy a dedicated recovery system. The
al ternat ive t o individual t reatment systems fo r m e t a l recovery would be a
central ized waste t reatment faci l i ty , where the wastes could b e
col lect ively treated. In such a faci l i ty , the recovery options would be more
economically at t ract ive. Such central ized t reatment faci l i t ies are in
operation in West Germany.
o E f fec t i ve dewatering of the solids.
Solids are dewatered by some fac i l i t ies using a f i l te r press, By ef fect ive ly
dewatering the solids, the quant i ty of waste sent f o r landfi l l ing can be
decreased by about 50 percent (AESI 1981). More e f fec t i ve dewatering can
be achieved using disc, scroll, or basket type centrifuges, vacuum drums or be l t f i l ters.
3 86 - 2 5
. ..
9.1.4 Spills and Leaks
Spills a r e the result of overflow from various process tanks and o ther inadvertent discharges, such a s valve closure failure, leaky gaskets, and drips. The following source reduction method is postulated:
o Bet te r operating practices. By using splash guards and drip boards, spilled liquids can be recycled and spilled cleaning wastes can be avoided. Use of f loa t valves or a la rm systems a re inexpensive options to prevent overflows. Other possibilities include liquid level controllers. Good housekeeping m e a w r s s such as periodic inspection of process equipment and piping, periodic relining of
the tanks, and training and educating personnel to be cognizant of t he importance of controlling waste generation can reduce the number and s ize of spills and leaks occuring in a facility.
9.1.5 Stripping Wastes
Stripping wastes, which a r e generated most commonly in small job shops, a r e the result of removing old or bad coatings on objects prior t o the required sur face finishing operation. The operation is essentially an etching type t r ea tmen t , whereby the coat ing is dissolved in an acid. Since the same bath may b e used to s t r ip various me ta l objects, this waste is difficult t o deal with since recycling or regeneration is not generally possible. The following source reduction techniques a r e suggested:
o Use of non-chrome etchants. Whenever possible, fe r r ic chloride, or ammonium persulfate solutions should be used instead of chromic-sulfuric acid etchants. However, compatibil i ty with the planned surface t r ea tmen t must be carefully examined. The use of such e tchants will reduce the toxicity of t he stripping solution tha t ends up as a waste.
o Decrease the generat ion of off-spec coat ings t h a t require stripping.
9 6 - 2 6
L L, J
( ' 1 these streams tncluded l i s t e d * f * and/or 'K' RCRA wastes
9.2 Implementation Prof i le
The source control methods discussed for use by the meta l surface finishing industry
have d i f ferent potentials for appl icat ion depending on whether the fac i l i ty is a capt ive
shop or a job shop, Job shops are usually required by the i r cl ientele to fo l low cer ta in
operating procedures, and most job shops buy their process solutions f rom
manufacturers. Thus, modif icat ions in certain operating procedures and changes in
process solutions are not feasible in many job shops without the guidance and approval
o f the customer. Also, because smaller operations usually have space l imi tat ions,
instal lat ion of additional tanks for countercurrent r insing may not be practical. For
faci l i t ies which have preprogrammed hoist lines in operation, changes in operations
such as rinsing may be d i f f icu l t . However, measures such as the instal lat ion o f f l o w
control valves, splash guards, etc., which do not require much capi ta l or space can be
used by a l l facilities. E f f i c ien t use of water can be made by reusing spent process
water a t places that require low qual i ty water. Improvements in operating practices,
such as spi l l and leak prevention, are addit ional measures which require l i t t l e capi ta l
t o implement. 8
Reclamation of metals f r o m wastes is
hazardous constituents of these wastes.
) an e f fec t i ve way to reduce or el iminate the
In many job shops, the volume o f wastes may
be too low for economical recovery of metals. I n such cases, the use of central ized
waste treatment fac i l i t ies t o co l lect and t rea t wastes f r o m various plants has proven
in some t o be a long-term economical solution.
9.3 Summary
The summary of a l l noted source contro l techniques i s given in Table 9-1. Each
technique was rated for i t s effectiveness, extent o f current use and future appl ication
potent ia l on scale of 0 t o 4. The rat ings were derived by project s ta f f based on rev iew
o f the available data and in consultat ion w i t h the industry. The estimates of current
level o f waste reduction achieved (current reduction index) and possible future
reduction ( future reduction index) were obtained f rom the rat ings in accordance w i t h
the methodology presented in the introduct ion t o this appendix.
8 6 - 2 8
-> The current reduction index (CRI) is a measure of reduction of waste tha t would be generated i f none of the methods listed were implemented to the i r current level of
application. For t h e en t i re metal surface finishing industry, CRI is 1.0 (25 percent) which is indicative of the low to modera te level of waste minimization tha t already has taken place. Current measures tha t have proven effective as a whole have been the use of less toxic bath solutions, t he reuse and recycling of spent rinse water , t h e reclaiming of meta l f rom waste, and the implementation of b e t t e r operating pract ices ,
The future reduction index (FRI) is an indication of t h e level t o which the current ly generated waste can be reduced if a l l of t h e techniques noted were implemented according to their ra ted potential. The FRI value of 0.7 t o 1.3 (18 t o 33 percent) is indicative of the moderate ex ten t of fu ture waste reductions. Among the techniques tha t were found most effective and applicable (as evidenced by high FRI value), employment of effective rinsing methods, metal /acid recovery f rom spent baths, use
of more dilute process solutions, and fur ther implementation of be t t e r operating prac t ices appear t o promise the grea tes t level of reduction for t h e industry a s a whole.
10. PRODUCT SUBSTITUTION ALTERNATIVES 1 Since many meta l objects can be coa ted with several a l ternat ive meta ls to achieve t h e
same quality of t rea ted surface, cer ta in substi tutions could contr ibute towards hazardous waste reduction. The replacement of nickel by zinc is possible in some instances. In other applications, zinc can b e substi tuted by manganese or iron. Electroless nickel plating, used by some printed circui t boards manufacturers , can be subs t i tu ted with electroless copper plating. Cadmium and silver can generally be
subs t i t u t ed with o ther metals.
11. CONCLUSIONS
The es t imates indicate tha t moderate reduct ions of waste generated by the metal sur face finishing industry are possible, probably in t h e 18 t o 33 percent range. Several
e f fec t ive source control measures include use of eff ic ient rinsing techniques, recovering metal/acid f rom spent baths, use of more dilute process solutions and fur ther im9lementation of b e t t e r operating practices.
R 6 - 29
12. REFERENCES
AESI. 1981. American Electroplater 's Society, Inc. Conference on advanced pol lut ion contro l for the meta l finishing industry. EPA-600-2-81-028. Cincinnati, Ohio: U.S. Environmental Protect ion Agency.
Alban, L.E. 1981. M e t a l surface treatments: case hardening. In Ki rk-Othmer Encyclopedia of Chemical Technology. 3rd ed. Vol. 15, pp. 313-24. New York, N.Y.: Wiley.
Arienti , 14. 1985. GCA Corporation. Waste category assessment report, Solvent waste: draf t f inal report. EPA Contract No. 68-03-3243. Cincinnati, Ohio: U.S. Environmental Protect ion Agency.
Basta, N. 1983. Tota l m e t a l recycle i s meta l finishers' goal. Chemical Enqineerinq. 90(10)816-19.
Basta, N. 1984. Ion-beam processing: new surface treatment method. Chem. Process. 91(16): 18-21.
BCL. 1976. Batel le Columbus Lab. Assessment o f industr ial hazardous waste practices: e lectroplat inq and meta l finishinq industr ial job shops. EPA-530-SW-136C. Washington, D.C.: U.S. Environmental Protect ion Agency.
Campbell, M.E., and Glenn, W.M. 1982. P r o f i t f rom pol lut ion prevention. Ontario, Canada: Pol lut ion Probe Foundation.
Chementator. 1982. Chemical Enqineerinq. 89(14):9-10.
Cook, T.M., Cubbage, M.L., and Fister, L.J., 1984. sheets, baskets, pipes, threads and fins, Meta l Finishing, (7):33.
C.P. Staff. 1984. Hexavalent chromium waste detoxif ied by chemical system, dewater through f i l t e r press. Chem. Process. 47(10):38.
Durney, L.J., ed. 1984. Electroplat inq enqineerinq handbook. 4 th ed. New York, N.Y.: Van Nostraud Reichold Co.
Draining process solutions from
Lane, C., 1985. Fluorocarbon coating el iminates corrosion o f acid bath racks. Chem. Process. 48(10): 72.
Lewis, T.A. 1980. Ind. Finish. A p r i l 1980.
Ma thews, J.E. 1980. Industr ial reuse and recycle of wastewater: l i terature review. Robert S. K e r r Environmental Research Lab. EPA-600-2-80-183. Ada, Okla: US. Environmental Protect ion Agency.
Olsen, A.E. 1973. Upgrading meta l finishinq faci l i t ies to reduce pollution. Oxy M e t a l Finishincl Operation. EPA-625-3-73-002 (USEPA Technology Transfer). Washington, D.C.: U:S. Environmental Protect ion Agency.
Schneberger, G.L. 1981. Metal sur face t reatments: chemical and electroplat ing conversion t rea tment . In Kirk-Othmer encyclopedia of chemical technoloqy. 3rd ed. Vol. 15, pp. 304-12. New York, N.Y.: Wiley.
UNECE. 1982. United Nations Economic Commision for Europe. Compendium on low and non-waste technoloqy. Vol. 4. Monograph 73. Geneva: United Nations Economic Commission for Europe.
USC. 1983. U.S. Congress, Off ice of Technology Assessment. Technoloqies and manaqement s t ra teq ies for hazardous waste control. Washington, D.C.: U.S. Government Printing Office.
USEPA. 1980. U.S. Environmental Protect ion Agency, Off ice of Water Regulations and Standards. Development document for eff luent limitation: quidelines and s tandards for t he me ta l finishing industry. EPA-440-1-80-091A. Washington, D.C.: U.S. Environmental Protect ion Agency.
. 1981. U.S. Environmental Protect ion Agency, Industrial Environmental Research Lab. Implement chanqes for meta l finishers. Cincinnati , Ohio: U.S. Environmental Protect ion Agency.
. 1982. US. Environmental Protect ion Agency, Eff luent Guidelines Division. Development document for eff luent limitations: quidelines and standards for the coil coat ing industry. EPA-440-1-82-071. Washington, D.C.: U.S. Environmental Protect ion Agency.
Versar, Inc. 1985. Versar. National Profiles Report for Recyclinq/a preliminar assessment, D r a f t report for waste t r ea tmen t branch, EPA Cont rac t No. 68-01-7053: U.S. Environmental Pro tec t ion Agency.
1
13. INDUSTRY CONTACTS
Dr. J. Chu, Environmental Activit ies Staff , General Motors Corp., Warren, W.
D. Anzures, National Association of Metal Finishers, San Fernando, CA.
W.G. Vaux, P.E., Chemical and Process Engineering, Westinghouse Electr ic Corp., Pit tsburgh, PA.
