INSPECTION Procedure for Galvanizing

8/20/2019 INSPECTION Procedure for Galvanizing

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THERMAX LIMITED

CHINCHWAD PUNE – 411019, INDIA

B & H QUALITY ASSURANCE & CONTROL PROCEDURES

INSPECTION PROCEDURE FOR CONTROL NO : HDG/ GCP/ 01

GALVANIZING RE VISION : 0 DATE : 27/ 12/2013

PAGE NO : 1 OF 14

1.0 SCOPE

This specification define the minimum requirement for the surface preparation material supply& application of paint for coating of onshore plant steel structure, piping, vessel, equipment &accessories.

2.0 Procedure Format

3.0 Importance4.0 Flow hart of !ot "ip #alvani$ing %rocess.0 #alvani$ing %rocess'.0 (tandard )perating ycle Time*.0 Type of Inspection+.0 epair %rocedure

3.0 Importance

In this type of coating application, surface is protected with molten $inc with --.- of $incpurity . To %rovide the protection from atmospheric conditions. !"# coating is high corrosionresistance & %rovide higher dura/ility life.

4.0 Flow Chart of Hot Dp !al"an#n$ Proce%%

1 )ptional for articles contaminated /y )il, #rease 22 De$rea%n$"ipping in "egreasing solution1

1 "ipping in !ydrochloric acid /ath at am/ient temperature 22 Pc&ln$ to scour the steel surface and remove any rust or scale

3' To remove e5cess 6cid neutrali$e its effect and o/tain a clean surface 7 (n%n$

4' (olution of 8inc 6mmonium hloride to ensure efficient flow 22 Flu)n$ of 8inc over the surface to ensure good /onding

1 To remove unwanted moisture and increase the steel temperature 22 Dr*n$ Dec& to required level for compete coating

'1 9ath of molten 8inc in a temperature range of 4': 2 4'0: . 22 !al"an#n$ %roduct is gradually withdrawn to allow e5cess 8inc to drain off.

*1 For ooling with cold water 22 +uenchn$

+1 To prevent formation of white rust. 22 Dchromatc


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,.0 !al"an#n$ Proce%%

. 6fter visual inspection of /lac; material lift the material with the help of crane.

. "ip the material in degreasing /ath.


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-.0 Standard Operatn$ C*cle me

SR

No. PROCESS

STANDARD

TIME MAX TIME(FOR 120

MIC)

MAX TIME(FOR 86

MIC)MIN MAX

1

LOADING POINT TO PICKLING

TANK2 3 2 2

2DIP TIME IN PICKLING TANK No.1

10 20 15 15

3LIFT & TITLT TIME IN PICKLING 1

2 2 2 2

4DIP TIME IN PICKLING TANK No.2

10 20 15 15

5

LIFT & TITLT TIME IN PICKLING 2

2 2 2 2

6

DIP TIME IN PICKLING TANK No.3

10 20 15 15

7

LIFT & TITLT TIME IN PICKLING 3

2 2 2 2

8

DIP TIME IN RINSE 1 & 2.

4 4 4 4

DIP TIME IN FL!"

2 2 2 2

10

DR#ING TIME ON $OT PLATE

10 10 10 10

11 DIP TIME IN %INC AT$ 2 5 4 2

12

LIFT & TILT TIME IN %INC AT$

2 2 2 2

13

DIP TIME IN '!ENC$ING

2 2 2 2

14DIP TIME IN DI C$ROMATING

2 2 2 2

TOTAL TIME (min.) 38 52 45 43

PREPARED BY CHECKED BY APPROVED BYTHERMAX LIMITED




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/.0 *pe Of In%pecton

The type of inspections performed on hot2dip galvani$ed steel. These techniques for

each test method are specified in 6(T> 6 3=6 3>, 6 3=6 3>, or 6 *'*=6 *'*>,

depending upon the type of product /eing inspected. The most common inspections,

listed /elow, range from a simple ?isual Inspection to more sophisticated tests to

determine em/rittlement or adhesion.

1 oating Thic;ness #auge 7 magnetic gauges,1 oating @eight 7 alculation of >ass )f 8inc31 %reece Test 7 uso4 Test

41 !ammer Test

.0 %ual In%pecton

Finish and 6ppearance 7 visual inspection

are Spot%F!"#$ 1

9are spots, defined as uncoated areas on the steel surface, are the most common surface defectand occur /ecause of inadequate surface preparation, welding slag, sand em/edded in castings,e5cess aluminum in the galvani$ing ;ettle, or lifting aids that prevent the coating from forming in asmall area. )nly very small areas, less than inch in the narrowest dimension with a total of nomore than 0.of the accessi/le surface area, may /e renovated using 6(T> 6 *+0. This meansnarrow, /are areas may /e repairedA however, if they are greater than one inch2square areas, the

product must /e re2galvani$ed.


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In order to avoid /are spots, li;e those seen in Figure 1, the galvani$er must ensure the surfaces

are clean and no contaminants are present after pretreatment. If the si$e of the /are spot or total

surface area causes reBection, the parts may /e stripped, re2galvani$ed, and then re2inspected for

compliance to the standards and specifications.

Chan and re ar&%F!"#$ % C'() ()* W#$ M(#+

6nother type of surface defect occurs when steel is lifted and transported around the galvani$ing

plant using a chain or wire. These lifting aids can leave uncoated areas on the finished product that

will need to /e repaired. The superficial mar;s, li;e those seen in Figure 2 , left on the galvani$ed

coating from the lifting attachments are not grounds for reBection as long as mar;s can /e

repaired. 6(T> specifications do not allow any /are spots on the finished galvani$ed part.

F!"#$ - Delmtaton

"elimitation or peeling creates a rough coating on the steel where the $inc has peeled off. There

are a num/er of causes for $inc peeling. >any large galvani$ed parts ta;e a long time to cool in the

air and form $inc2iron layers after they have /een removed from the galvani$ing ;ettle.THERMAX LIMITED




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This continued coating formation leaves /ehind a void /etween the top two layers of the galvani$edoating. If there are many voids formed, the top layer of $inc can separate from the rest of thecoating and peel off the part. If the remaining coating still meets the minimum specificationrequirements, then the part is still accepta/le. If the coating does not meet the minimumspecification requirements then the part must /e reBected and re2galvani$ed. If delimitation, as seenin Figure 3, occurs as a result of fa/rication after galvani$ing, such as /lasting /efore painting, thenthe galvani$er is not responsi/le for the defect

D%tortonF!"#$ 4 D./#./)"istortion, as seen in Figure 4, is defined as the /uc;ling of a thin, flat steel plate or other flat

material such as wire mesh. The cause of this is differential thermal e5pansion and contraction rates

for the thin, flat plate and mesh than the thic;er steel of the surrounding frame. In order to avoid

distortion, use a thic;er plate, ri/s, or corrugations to stiffen flat sections or ma;e the entire

assem/ly out of the same thic;ness steel. "istortion is accepta/le, unless distortion changes the

part so that it is no longer suita/le for its intended use.

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Drana$e Sp&e%F!"#$ D#()(!$ S+$

"rainage spi;es or drips are spi;es or tear drops of $inc along the /ottom edges of the product.

These result when the surfaces of the product are processed hori$ontal to the galvani$ing ;ettle,

preventing proper drainage of the $inc from the surface as the product is withdrawn from the ;ettle.

"rainage spi;es, as seen in Figure 5 , are typically removed during the inspection stage /y a /uffing

or grinding process. "rainage spi;es or drips are e5cess $inc and will not affect corrosion protection,

/ut are potentially dangerous for anyone who handles the parts. These defects must /e removed

/efore the part can /e accepted.

Dro%% Inclu%on%F!"#$ 2 D#/ I)3"/)

"ross inclusions are a distinct $inc2iron intermetallic alloy that /ecomes entrapped or entrained inthe $inc coating. This is caused /y pic;ing up $inc2iron particles from the /ottom of the ;ettle. "ross,as seen in Figure 6 , may /e avoided /y changing the lifting orientation or redesigning the product to

allow for proper drainage.

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If the dross particles are small and completely covered /y $inc metal, they will not affect the

corrosion protection and are accepta/le. If the dross particles are large, then the dross must /e

removed and the area repaired.

E)ce%% 5lumnum n !al"an#n$ athF!"#$ 5 E63$ A"7)"7 ) 8(():)! B(.'

6nother type of surface defect, shown in Figure 7 , is caused /y an e5cess amount of aluminum inthe galvani$ing /ath. This creates /are spots and /lac; mar;s on the surface of the steel. Thee5cess aluminum can /e avoided /y ensuring proper control of the aluminum level in thegalvani$ing /ath /y means of regular sampling and analysis, and /y adBusting the levels in a regularand controlled manner. For small areas of /are spots, the part may /e repaired as detailed in thespecification. If this condition occurs over the entire part, then it must /e reBected and re2galvani$ed

F!"#$ ; F%h onn$ Fish /oning is an irregular pattern over the entire surface of the steel part. This is caused /ydifferences in the surface chemistry of a large diameter steel piece and variations in the reactionrate /etween the steel and $inc. These reaction differences cause the thic;ness of the galvani$edcoating to vary in sharply defined $ones across the surface. Fish /oning, has no effect on thecorrosion protection provided /y the $inc coating and is not cause for reBection of the hot2dip

galvani$ed part.

THERMAX LIMITED




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Fla&n$F!"#$ 9 M3#/!#(' /< F(+)!

Fla;ing results when heavy coatings develop in the galvani$ing process, usually mils or greater.

This generates high stresses at the interface of the steel and the galvani$ed coating and causes the

$inc to /ecome fla;y and separate from the surface of the steel. Fla;ing can /e avoided /y

minimi$ing the immersion time in the galvani$ing ;ettle and cooling of the galvani$ed steel parts as

quic;ly as possi/le. Figure 9 shows a micrograph of fla;ing. In addition, using a different steel

grade, if possi/le, may also help avoid fla;ing. If the area of fla;ing is small, it can /e repaired and

the part can /e acceptedA however, if the area of fla;ing is larger than allowed /y the specifications,

the part must /e reBected and re2galvani$ed.

Flu) Inclu%on%F!"#$ 10 F"6 I)3"/)

Flu5 inclusion can /e created /y the failure of the flu5 to release during the hot2dip galvani$ing

process. If this occurs, the galvani$ed coating will not form under this flu5 spot . If the area is small

enough, it must /e cleaned and repairedA otherwise, the part must /e reBected. Flu5 spots canincrease if the flu5 is applied using the wet galvani$ing method which is when the flu5 floats on the$inc /ath surface. Flu5 deposits on the interior of a hollow part, such as a pipe or tu/e, as seenin Figure 10 , cannot /e repaired, thus the part must /e reBected.THERMAX LIMITED




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6ny flu5 spots or deposits, pic;ed up during withdrawal from the galvani$ing ;ettle do not warrant

reBection if the underlying coating is not harmed, and the flu5 is properly removed.

O)de 6ne%F!"#$ 11 O6*$ L)$

)5ide lines are light colored o5ide film lines on the galvani$ed steel surface. )5ide lines are caused

when the product is not removed from the galvani$ing ;ettle at a constant rate. This may /e due to

the shape of the product or the drainage conditions. )5ide lines, as seen in Figure 11, will fade over

time as the entire $inc surface o5idi$es. They will have no effect on the corrosion performanceA only

the initial appearance will /e affected. This condition is not a cause for reBection of the hot2dip

galvani$ed parts.

Surface ContamnantF!"#$ 1% S"#


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If they result in /are areas, then the repair requirements apply and small areas may /e repaired, /ut

a large area is grounds for reBection and the entire part must /e re2galvani$ed.

ouch ar&%F!"#$ 1- T/"3' M(#+

6nother type of surface defect is ;nown as touch mar;s, which are damaged or uncoated areas on

the surface of the product. Touch mar;s are caused /y galvani$ed products resting on each other or

/y the material handling equipment used during the galvani$ing operation. Touch mar;s, as seen in

Figure 13, are not cause for reBection if they meet the si$e criteria for repaira/le areas. They must /e

repaired /efore the part is accepted.

7nc S&mmn$F!"#$ 14 =)3 S+77)! I)3"/)

(;imming deposits are usually caused when there is no access to remove the s;imming during thewithdrawal of the steel from the galvani$ing ;ettle. The s;imming on the liquid $inc surface aretrapped on the $inc coating. In order to remove $inc s;imming without harming the soft $inc coatingunderneath, lightly /rush them off the surface of the galvani$ed steel during the in2house inspectionstage with a nylon2/ristle /rush. 8inc s;imming, as seen in Figure 14, are not grounds for reBection.

The $inc coating underneath is not harmed during their removal and it meets the necessaryspecifications.

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7nc Splatter F!"#$1 =)3 S(..$#

8inc splatter is defined as splashes and fla;es of $inc that loosely adhere to the galvani$ed coating

surface. 8inc splatter is created when moisture on the surface of the galvani$ing ;ettle causes liquid

$inc to CpopD and splash droplets onto the product. These splashes create fla;es of $inc loosely

adherent to the galvani$ed surface. 8inc splatter, as seen in Figure 15 , will not affect the corrosion

performance of the $inc coating and is not cause for reBection. The splatter does not need to /e

cleaned off the $inc coating surface, /ut can /e if a consistent, smooth coating is

required.

THERMAX LIMITED




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.0 (epar Procedure

The coating thic;ness of the repaired area must match the coating thic;ness of the surrounding

area. !owever, if $inc2rich paint is used for repair, the coating thic;ness must /e 0 higher than

the surrounding area, /ut not greater than 00 microns /ecause mud crac;ing tends to result when

the paint coating is too thic;. The ma5imum si$es for allowa/le areas that can /e repaired during in2

plant production are defined in the specifications as summari$ed /elow.

61 a)mum S#e of (epara8le 5rea

5S 5 12395 123:

)ne inch or less in narrowest dimension. Total area can /e no more than 0. of the accessi/le

surface area to /e coated or 3' square inches per piece, whichever is less

5S 5 1,395 1,3:

The /are spots shall have an area totaling no more than of the total surface area to /e coated,

e5cluding threaded areas of the piece

5S 5 /-/95 /-/:

Eo area given

If the coating fails to meet the requirement for finish and adherence, the /ar may /e stripped, re2galvani$ed, and resu/mitted

"amage done to the coating due to fa/rication or handling shall /e repaired with a $inc2richformulation

(heared ends shall /e coated with a $inc2rich formulation

THERMAX LIMITED




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91 (epar ethod%

The touch2up and repair materials are formulated. >aterials used to repair hot2dip galvani$ed

products include $inc2/ased solder, $inc2rich paint, and $inc spray metali$ing, and are e5plained in

the following sections.

7nc;(ch Pant

8inc2rich paint is applied to a clean, dry steel surface /y either a /rush or spray asseen in Figure 56 , and usually contains an organic /inder pre2mi5. 8inc2rich paintsmust contain either /etween ' to '- metallic $inc /y weight or greater than -metallic $inc /y weight in dry film. %aints containing $inc dust are classified as organicor inorganic, depending on the /inder they contain. Inorganic /inders are particularlysuita/le for paints applied in touch2up applications around and over undamaged hot2

dip galvani$ed areas.1 Surface Preparaton

6ccording to 6(T> 6 *+0, the surface to /e repaired shall /e /last cleaned to ((%2(%0=E6

Eo. near white metal for immersion applications and ((%2(% for less aggressive field

conditions. @hen /lasting or power tool cleaning is not practical, hand tools may /e used to clean

areas to /e reconditioned. The /last cleaning must e5tend into the surrounding, undamaged,

galvani$ed coating.

D' 5pplcaton

This method of repairing galvani$ed surfaces must ta;e place as soon as possi/le after preparationis completed and prior to the development of any visi/le o5ides. The spraying or /rushing should /ein an application of multiple passes and must follow the paint >fg. specific written instructions. In

addition, proper curing of the repaired area must occur /efore the product is put through the finalinspection process. This repair can /e done either in the galvani$ing plant or on the Bo/ site and isthe easiest repair method to apply /ecause limited equipment is required. 8inc2rich painting should/e avoided if high humidity and=or low temperature conditions e5ist /ecause adhesion may /e

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INSPECTION Procedure for Galvanizing

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