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11/27/13 Hydrogen Embrittlement in Plating www.finishing.com/1200-1399/1216.shtml 1/17 HOME / sitemap FAQs BOOKS Help Wanteds Advertise Contact you are here: Hotline/Forum => Letter 1216 Search Hydrogen Embrittlement in Plating - - - - A series of Questions about hydrogen embrittlement in plating, Answered by dozens of experienced experts - - - - ---- Q. We have had problems with a metal clip, and it is said to be due to "hydrogen embrittlement". What is hydrogen embrittlement, and how do you avoid/alleviate it? Michael Marshall Indianapolis, Indiana ---- A. Hydrogen embrittlement is a phenomenon that affects high-strength steel. Hydrogen--often from pickling or plating--invades the grain structure of a high strength steel, making it brittle and subject to catastrophic failure. The best approach is to avoid or minimize processes that cause hydrogen embrittlement. The second best approach is to bake the parts to drive the hydrogen out, preferably very soon after plating. Some people feel that some degree of permanent damage occurs during the time between plating and baking, and that it is thus vital to bake immediately. Others feel that the old standard "bake within 24 hours" is sufficient. ASTM Committee B-8 spent a lot of time on this problem, so I think their specs are highly trustable. Ted Mooney, P.E. RET finishing.com Brick, New Jersey nanodiamond web-sales www.carbodeon.com High-quality nanodiamond materials as powders and dispersions
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Page 1: Hydrogen Embrittlement in Plating

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HOME / sitemap FAQs BOOKS Help Wanteds Advertise Contact you are here: Hotline/Forum => Letter

1216

Search

Hydrogen Embrittlement in Plating

- - - - A series of Questions about hydrogen embrittlement in plating, Answered by

dozens of experienced experts - - - -

----

Q. We have had problems with a metal clip, and it is said to be due to "hydrogen embrittlement".

What is hydrogen embrittlement, and how do you avoid/alleviate it?

Michael MarshallIndianapolis, Indiana

----

A. Hydrogen embrittlement is a phenomenon that affects high-strength steel. Hydrogen--often

from pickling or plating--invades the grain structure of a high strength steel, making it brittle andsubject to catastrophic failure.

The best approach is to avoid or minimize processes that cause hydrogen embrittlement. Thesecond best approach is to bake the parts to drive the hydrogen out, preferably very soon afterplating. Some people feel that some degree of permanent damage occurs during the timebetween plating and baking, and that it is thus vital to bake immediately. Others feel that the oldstandard "bake within 24 hours" is sufficient. ASTM Committee B-8 spent a lot of time on thisproblem, so I think their specs are highly trustable.

Ted Mooney, P.E. RETfinishing.comBrick, New Jersey

nanodiamond web-saleswww.carbodeon.com

High-quality nanodiamond materials as powders and dispersions

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----

A. Michael: We have had some experience with the phenomena of hydrogen embrittlement.

A good reference book is Hydrogen Embrittlement and Stress Corrosion Cracking [link is

to info about book at Amazon] by Gibala and Hehemann (ASM Publication). It is quite detailed andinformative.

Brian CardwellFord Motor Company

.

Q. I am looking for any reference information about hydrogen embrittlement (mechanism).

nina

- Halifax, Canada

----

Q. I am looking for articles on "Hydrogen Embrittlement" in the plating process.

John M. GrimesCutler-Hammer

----

A. Over the years, the Airline Plating Forum has had several papers given on the subject.

Available thru the AESF bookstore. There is a stray article in the plating magazines. Seems tome that the big book ASM library had some information on it. You might check the index for thevarious Sur-Fin abstracts. These probably will be more technical and less practical.

James Watts

- Navarre, Floridamisc. plating stuffFor Sale cheap

.

A. There are many good books on this subject that you can research for your project, Nina. If

hydrogen embrittlement related to metal finishing is your issue, Jack Dini's "Electrodeposition -The Materials Science of Coating and Substrates" has a very interesting chapter on themechanism.

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Ted Mooney, P.E. RETfinishing.comBrick, New Jersey

.

A. The basic situation is one little hydrogen atom lost inside the metal matrix (crystal), it takes

up almost no room, can move easily through the crystal and causes very little stress to thecrystal structure.

Then it meets another hydrogen atom, they're dead happy to meet each other and join tobecome one molecule of hydrogen gas. Gas takes up about 1000 times the volume, so themolecule puts a lot of localised stress on the crystal, a few more molecules in a few moreplaces and then the trouble starts.

Ian Brookeuniversity - Glasgow, Scotland

--

Q. During plating, are the corners of objects preferential sites for hydrogen and therefore more

susceptible to hydrogen embrittlement?

David M. French

Charlotte North Carolina

--

A. Yes and no. Since the edges (corners) are high current density

areas, they plate much faster, so more H2 is generated there, so it will bea little more prone to problems there. In high stress deposits, the additionalthickness puts the parent material under a lot more stress, so will tend tohave more problems there.

A stress riser like a tiny cut from a razor blade in masking on a high tensilestrength part will be much more prone to fail. Inadequate radius at flangesare very prone to failure. The end result is a failed part, but the root causesare wildly different.

James Watts- Navarre, Florida

misc. plating stuffFor Sale cheap

Current Solutions toHydrogen Problems in

SteelsInterrante &Pressouyre

--

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A. The amount of Hydrogen Embrittlement absorbed during electroplating is related to the

current density on the cathode surface of the article being plated. Higher current density areaswill evolve more Hydrogen gas and therefore the potential for embrittlement is higher. Edges willnormally be higher current density than flat surfaces. Edges that are on bottom rows of racks willmost likely have higher levels of absorbed Hydrogen. In most cases of electroplating, edges willhave higher preferential sites for Hydrogen Embrittlement. Maintaining optimum electroplatingefficiencies and additions of wetting agents are variables that can help reduce embrittlement byHydrogen gas.

Bill BoatrightMorrisville, North Carolina

---

A. Higher current densities will definitely produce more hydrogen per metal deposited, but...

Some processes (for sure low embrittlement cadmium, but maybe some others too?) use highcurrent densities on purpose in order to produce porous plating that allows for easy hydrogenmolecule escape during the subsequent bake.

In general I do not think that areas where most of the hydrogen is absorbed would suffer higherdanger of embrittlement: metal is a "transparent" media for protons (hydrogen atom's nucleus),therefore the bulk of the plated part (even the non-plated part of it, if masked) will be equallyprone to embrittlement.

The question remaining - where it may break? - in the point of maximum stress, even if thatportion of the part is not plated.

This is just an opinion...

Max Steincaptive metal finisher - Montreal, Québec, Canada

--

Q. How does one determine if breakage is caused by hydrogen embrittlement? We have

parts which are made from 1074 steel, .0135" thick, which has been formed (into a question markshape) and then heat treated to RC 44-47. These parts can be bent without breakage. However afterzinc and bake, they do break when bent pretty far back in the large radius area.

How does one determine if the breakage is caused by hydrogen embrittlement? Or is it possible thatjust by plating these parts, they will become more prone towards breakage?

Andrew Robertssprings - San Leandro, California

--

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A. If you had access to a Scanning Electron Microscope (SEM) and someone with

experience in analyzing for Hydrogen Contamination it could be possible to show breakagewas caused by Hydrogen Embrittlement.

However, since you say the parts are not breaking before plating but are breaking after, thepossibility is strong that hydrogen embrittlement is occurring in your parts. Have you baked theparts for hydrogen embrittlement relief immediately after plating and before bending.

Greg Haataja

helicopters - Fort Worth, Texas

--

A. You have about as close to 100% probability as you will ever get that you have a classic

H2 embrittlement problem.

Bake as soon as possible after plating. The longer the H2 is trapped between the plate and thebase metal, the further it penetrates the steel and the harder it is to get out.

Do not flex the parts even a tiny bit taking them off the rack!

If you are baking, get there sooner and bake longer or at a higher temp.

After bake a very quick dip in a mild (weak) nitric solution will activate it enough that it will take achromate. Consult your chromate vendor and do some trial and error testing to see how weakyou can get by with.

James Watts- Navarre, Florida

--

A. A considerable amount of work on hydrogen embrittlement has been conducted and

published in the literature. Some important work was done and published by scientists at theNaval Air Warfare Center. The bottom line is: it is nearly impossible to remove all of thehydrogen that has been introduced, using common baking methods. Once the damage is done,it can be reduced to some extent. The amount of damage and reduction will depend on dozensof variables such as the part, its material, coating, process, amount of hydrogen generated andabsorbed and combinations thereof. Relief is likely to be inconsistent. This inconsistency couldbe reduced by porosity in the coatings.

Mandar Sunthankar- Fort Collins, Colorado

--

A. Hydrogen embrittlement is typically manifested as "delayed fracture" at static stresses,

which would be contrary to immediate failure during bending. Your parts, however, are quite

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susceptible to hydrogen damage and may be cracked during plating if the parts have sufficientresidual stress from heat treating. A static load test with less deflection than will causeimmediate cracking could be definitive.

Another alternative to consider is possible embrittlement due to the baking process. Thismaterial is susceptible to tempered martensite embrittlement, usually from exposure totemperatures from 400 °F to 700 °F. I would avoid baking at temperatures above 375 °F.

I agree with Mr. Sunthankar that baking is not 100% effective. The extreme susceptibility of thismaterial to cracking by hydrogen embrittlement would suggest to me that an alternativecorrosion protection would be prudent.

Larry Hanke

materials testing laboratoryMinneapolis, Minnesota

Alternatives to Plating to Minimize HydrogenEmbrittlement

--

A. If hydrogen embrittlement is of concern, you may

want to consider mechanical plating and orgalvanizing. I have been involved in many studiescomparing zinc electroplating, hot dip galvanizing andmechanical and mechanical does not impart hydrogen.

Ray DeloreyCambridge, Ontario, Canada

adv.

++++++

A. One of the best systems for coating that do not have any hydrogen embrittlement

is the Thermal Diffusion zinc coating system. Google it and you'll learn quite a bit.

Dorian Shifman- Charlotte, North Carolina

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----Ed. note: Thermal Diffusion is a modern upgrade to the older process calledSherardizing, which is discussed in many threads on this site.

-

Q. Could you please let me know if there is a possibility for hydrogen embrittlement to be

introduced into my parts during this heat treat process:

Material: .012" +/- .001" C1050 Annealed Spring SteelHeat Treat: Austempered to Spring Temper Rc 38-42

I know that I have a hydrogen embrittlement problem induced by my plater due to improperlycalibrated ovens for baking off the hydrogen. I need to know if there are other ways for hydrogen to beintroduced into my stampings.

Adam Rubin- Brockton, Massachusetts

-

A. I really do not want to get in the middle of an argument, but will express my opinion.

I have never heard of hydrogen embrittlement being caused by bake.

Uncalibrated ovens probably did not contribute much to hydrogen embrittlement of your partsbecause bake relief is really wide open as a function of time and temperature. 375 °F for 4hours is + or - 25 °F as a common relief.

Two things cause more grief than a few degrees difference.

1. The time between plating and into the oven. For spring material is should be as soon aspossible. The 4 hour book value is really too long. The longer you wait, the harder it is to get outand the more damage has been done.

2. The acid activation or etch contributes more to embrittlement than the plating process does.For spring steel I would use periodic reverse or anodic electroclean followed by a very short,say 10 second dip in a conventional hydrochloric or sulfuric acid tank. I have done cyanide andacid cad without a failure of notch bar testing at some very high tensile strengths.

If these are not critical parts to safety, I would bake them for 24 hours, possibly 48 for betterreliability and use them. These are tiny parts that can be nicely run in a lab oven at a very lowcost with a decent recovery of the unbroken parts.

James Watts- Navarre, Florida

-

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A. To answer part of Mr. Rubin's question (can austempering cause hydrogen

embrittlement?):

I would say no, especially if the austenitizing (not the quenching) is done in salt. If theaustenitizing is done in an atmosphere furnace (typically endothermic gas at 40% H2), thensome hydrogen is absorbed by the metal. I suppose one could argue that this might cause HE. Iknow it can cause delayed quench cracking in parts quenched in media such as water or oil,and although hydrogen levels are probably much lower than in "classical" HE, it could be calledhydrogen embrittlement. I doubt very much that cracking would occur in an austempered partbecause the residual stresses and residual hydrogen levels are typically much lower due to thegentler quench rates and the residence time at the austempering temperature.

In other words, it's hard to imagine austempering causing HE, and I think most metallurgists andheat treaters would agree they've never identified such an occurrence or even suspected thepossibility.

John Ullman

-

Q. When 1050 material is processed to an Rc range of 40 - 48 and subsequently plated to

GM4345M commonly referred to as Phos & Oil, what is the correct practice with respect to bakingthis porous plating?

Is baking necessary, or is delay in use after plating sufficient to allow the H2 to outgas? If delay issufficient, what is the recommended period of time for delay?

What role does acid concentration play in processing the Phos & Oil in the cleaning tanks? Acommon standard seems to be to stay under 30%, is there a recommended concentration? What isit?, and is there a maximum that should not be exceeded to avoid hydrogen embrittlement?

Time in the tank is controlled to under 10 minutes.

L.C. WoodDetroit, Michigan

-

A. Bake- You have to conform to what the spec calls out.

Many specs would not call for a bake at an Rc of 40. I do not remember doing one at Rc48, socannot be of any help there.

Many people will not refer to phosphate as plating, since you are not depositing a metal or alloy.

Acid normally will be as strong as you need to do the job, but no stronger. Time is a tradeoff withacid strength. You have to specify the acid when you talk %'s. Sulfuric acid has two H's, so isbasically twice as strong as hydrochloric (muriatic). Some people use mixed acids.

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Acid etch is a major contributor to hydrogen embrittlement, so any etch should be the minimumto get by on hard parts.

If you use an acid etch, You really need to use a proprietary Ti compound additive to the lastrinse prior to phosphate. Normally, you will get a lousy phosphate if you do not. I have heard of avery few that have avoided it.

James Watts- Navarre, Florida

Is it possible to salvage parts that were not immediately

baked?

.

Q. Once parts have been determined to have hydrogen embrittlement failure, is there a way to

"save" the parts? I have heard several different theories from; the embrittlement can still be bakedout, to re-strip and re-plate the parts, to the parts are junk. Is there a definitive answer out there?

Kevin Almquist- Danielson, Connecticut

+++++++

Q. Please give advice on standard hydrogen de-embrittlement process. Please also advice on the

material which have bypassed hydrogen de-embrittlement process. How can we correct it?

PRABHUNATH SINGHHEAD FINISHING - ROHTAK, HARYANA, INDIA

.

A. Once the material is found to have a H/E problem, the micro-structure has already

sustained damage due to the "migration" of the trapped hydrogen (very small cracks). Re-working the parts will not correct the damage. This is only my opinion, but one based upon"ACTUAL" experiences related to H/E failures. My definitive answer would be "SCRAP" theaffected product, try to define and correct the "ROOT CAUSE" and try again. This has been myexperience.

TAIWAN Stainless Steelwww.lungan.com.tw

Stainless Steel, Coil, Plate, Bar Quality . Efficient . Innovation

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David L. Dowfastening systems - Automotive - Detroit, Michigan

First of two simultaneous responses -- +++++++

A. Prabhunath,

There is nothing that can be done to rescue parts that have missed de-embrittlement. Thedamage to the parts is time dependent and cannot be repaired, once the damage is done it ispermanent. It is made even worse that you probably won't even be able to tell whether the partshave suffered embrittlement damage so unfortunately you should scrap them.

De-embrittlement requirements across the world differ slightly but are usually based either onmaterial strength or material hardness (my particular company tends to work on strength).

As a rough guide (and I can only emphasise that it is a guide) materials below approximately1100 MPa (160 ksi) do not need de-embrittlement. Materials between 1100 MPa and 1450MPa (160-210 ksi) will need de-embrittlement at approximately 190-205 °C (375-400 °F) forabout 6 hours. Steels greater than 1450 MPa and less than 1800 MPa (210-260 ksi) will needde-embrittlement for about 18 hours at 190-205 °C, for greater than 1800 MPa then 24 hours isnormally recommended.

Just to make things more complicated materials with a low tempering temperature will beaffected by de-embrittlement at high temperatures so should be de-embrittled at 130-140 °C(265-285 °F) for 6 hours minimum. This also applies to carburised and induction hardenedparts. I'm sure there are other exceptions as well but they don't readily spring to mind at themoment.

I cannot think of a specification that is universally accepted as the de-embrittlement standard asevery OEM I have either worked for or have worked on their parts have always had slightlydifferent de-embrittlement requirements. If you are supplying to an OEM then you should usetheir specification; if you are the OEM then you should have a specification for de-embrittlementspecific to the materials that you commonly use.

Saying all that, I'm sure that I will be corrected and one of the many experts who contributeregularly to this site will come up with the relevant specification you require!

Brian TerryAerospace - Yeovil, Somerset, UK

Second of two simultaneous responses -- +++++++

A. Hydrogen de-embrittlement process is to let escape Nascent Hydrogen from the surface

of substrate which gets preferentially co-deposited with the basic deposit sought.For removing such nascent hydrogen, one has to subject the plated components to thetemperature of 210+/-10 °C for 2 to 6 hours within 4 hours of plating.

In case some components have bypassed such operation, it is a matter of whether Nascent

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Hydrogen prevails in such component. However, one raw method to know the presence ofHydrogen is to subject such item in Paraffin Wax preheated to 100 °C. If traces of bubbles arefound in the vicinity of immersed component, the Hydrogen De-embrittlement process wouldhave been by-passed.

Arvinda Kumar

Process Manager - Ghaziabad, UP, India

June 15, 2011

Q. Hi Aravind Kumar,

Any Standard or OEM Approved for the Paraffin test to conclude the Hydrogen deembrittlement test?

Kannan Boopathi- Salem, Tamilnadu, India

.

Q. Hello-

What's a good test to establish whether or not the failure is due to Hydrogen Embrittlement (forfittings)?

Is a sustained load test for 72 hrs with 85% max. allowable load a good criterion?

Fittings are made from 8740 steel, Heat treat to 170-190 ksi and CAD plated per QQ-P-416 [link is to

spec at TechStreet] and subsequently baked for 23 hrs.

KA

A Kamal- New York, New York

+

Q. I have conflicting reports from 2 test houses on analysis of screws with sheared heads. One

opinion is hydrogen embrittlement and the other is high core hardness. Is there a definite diagnosistool for hydrogen embrittlement.

James Wardle- Newcastle, UK

.

Q. I am doing a failure analysis on galvanized quench and tempered steel (.22C/1.32 Mn). I have

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read where the acid bath can cause hydrogen embrittlement in high-strength steels. Is it common tosee failure due to hydrogen embrittlement in quench and tempered steels (Yield strength = 116 ksi)?

David Reinhart- Longview, Texas

.

Q. I am interested in plating of metal parts and the hydrogen embrittlement that may occur and also

the relief of stress in such parts by baking.

Specifically, I ask if the stress relief occurs without baking and by the mere passage of time

and, if so, what time is normal or does the part remain capable of failure until baked?

If the metal parts plated are not stress relieved after plating, does the metal and/or the plating processpresent some danger of brittleness and/or failure?

Jim McBroom- Nashville, Tennessee

.

A. Hydrogen embrittlement does not relieve itself ever, because the problem is not the

presence of hydrogen (which I suppose might dissipate over time), it's the damage that thehydrogen did to the metal. Baking must be done very shortly after the embrittling process,preferably immediately.

Ted Mooney, P.E. RETfinishing.comBrick, New Jersey

+++++++

Q. I work in the fastener industry and this subject of hydrogen embrittlement comes up often

with parts that are plated.

Over a period of time won't the hydrogen bleed out, or has the damage been done and theparts are scrap?

Richard Jarret

fasteners - Itasca, Illinois

+++++++

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A. Hi, Richard. We appended your inquiry to a thread which answered it.

It's not the hydrogen that is the problem, it's the damage that the hydrogen has already done tothe steel. Good luck.

Ted Mooney, P.E. RET

finishing.comBrick, New Jersey

.

Q. Hello,

I am a student studying corrosion engr., I am presently studying hydrogen embrittlement, I like to knowabout the possible testing method of hydrogen embrittlement. If anybody can help me, I will reallyappreciate it. Thanks

B. Kannan

- India.

++

Q. Is there hydrogen after chromating or before that? When is produced hydrogen in a steel? Is the

appearance of hydrogen depending on the chrome on the steel or depend on the proper steel (tensilestrength?)

Alberto- Rosario, Santa Fe, Argentina

+++

A. Do you mean chromium plating?

Hydrogen enters steel during casting, cleaning by most common acids (except nitric), cathodicelectrocleaning, electroplating, heat treating in reducing atmospheres and some weldingprocesses. It can be a serious problem in highly stressed, high strength steels. There areseveral embrittlement mechanisms, but basically, the hydrogen adds to internal stresses andaccumulates at defects, leading to failure at even low loads. The hydrogen embrittlementdanger increases with increasing hardness and decreasing part thickness for a given type andamount of plating.

Hydrogen build-up is especially high in hard chromium plating from Cr+6 solutions due to thelow cathode efficiency (large amperage required). The amount of hydrogen liberated at thecathode (workpiece) surface is proportional to the plating thickness. Steel of ultimate tensilestrength 150 ksi or greater having residual stresses from machining, grinding, hardening, etc.,

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should be stress relieved or shot peened prior to plating. Steel having a tensile strength of atleast 160 ksi or HRC 36 shall be given a hydrogen bake-out at 191 °C (375 °F) or higher for 3or more hours as soon as possible after plating. See QQ-C-320B or AMS-QQ-C-320 [link is to

spec at TechStreet] CHROMIUM PLATING (ELECTRODEPOSITED), for more details.

Ken Vlach

- Goleta, California

Ken received a special"Contributor of the Year" awardfrom finishing.com for his numeroushelpful and well researched responses

-

Q. We manufacture and electroplate automotive safety hardware and are very well aware of the

"critical" stress relieving requirements. However, we also have a large volume of parts which are sub-contracted for E-coating that do not specify any stress relieving requirements. My question is: "Ifsimilar pre-cleaning cycles and materials are used for the cleaning of steel parts for electroplatingand/or e-coating, how come e-coated parts do not specify a post bake to relieve any possibilityof hydrogen embrittlement during the processing"? It appears to me that the temperature and timerequired to bake the paint film is not sufficient to remove induced hydrogen.

Rodney C. Todd, CEF

- Ontario, Canada

-

A. What kind of steel and what is the hardness? Usually embrittlement is not considered a

problem below Rockwell C-40 or 180 ksi, although some callouts go as low as C-30. How hotand how long is the bake cycle for your E-coat? Have you run any test specimens? We havefound tempered Belleville washers to be simple test pieces. Easily compressed and you canrun a large number for statistical reliability,

C.A.Smith

aerospace - Nashville, Tennessee

----

Ed. note: Thanks, C.A.! That Belleville washer idea is a great suggestion.

February 25, 2010

Q. Does zinc electroplating also affect the strength of the nuts? Surely a bolt would fail

somewhere outside the nut and thread. This question purely because Electro Galvanized Zinc Bluenuts do look so much better than mechanical plating.

Chris Vermaakracing - Heidelberg, Gauteng, South Africa

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February 25, 2010

A. Hi, Chris. Although failure of a nut sounds less likely than failure of a screw, I do not accept

the implication that failure won't happen in the nut. Picture the screw being made of highstrength steel and the nut being made of glass :-)

Electroplating has no effect on soft mild steel, but does cause hydrogen embrittlement of highstrength steel. Baking immediately after plating may solve the problem, but it may not -- astatistically valid testing regimen is necessary in order to know.

Regards,

Ted Mooney, P.E. RETfinishing.comBrick, New Jersey

November 6, 2013

Q. We clean parts in solvent with a pH value 10 to 11; it is definitely not acidic. But Army says it will

cause high strength steel hydrogen embrittlement. I just do not understand. You?

David Ho- Milford, Connecticut, USA ^- Privately contact this inquirer -^

November 11, 2013

A. Previous entries in this thread have alluded to the phenomenon which I will describe

forthwith: In electroplating, the article being plated is cathodic; and at this cathode, metal isdeposited. But there is also cathodic inefficiency in which hydrogen gas is generated; theelectroplating seals the hydrogen into the article being plated. So even if the parts never see apH below 7, there can still be hydrogen embrittlement.

P.S.: After reviewing this thread, I should add this postscript: A few inquiries asked how one canbe sure that failure is due to hydrogen embrittlement. One telling characteristic of hydrogenembrittlement is intergranular failure (metallurgists call it "rock candy"), which is clearly evidentunder strong magnification (roughly 500x or 600x). More rounded asperities in the fracture facewould contraindicate hydrogen embrittlement. I have seen respected testing laboratoriesconclude that plating + breaking = hydrogen embrittlement. That is sometimes the case, butsometimes not. You have to look at the fracture face.

Tom Rochester

Plating Systems & Technologies, Inc.

Jackson, Michigan, USA

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November 12, 2013

Very interesting postscript, Tom, which I had never heard before.

Regards,

Ted Mooney, P.E. RET

finishing.comBrick, New Jersey

November 18, 2013

A. There is a phenomenon known as caustic embrittlement and is commonly associated with

things that use very concentrated forms of caustic solution, or the solution is used under forcingconditions. I haven't seen anything that says pH 10-11 would be a problem unless you are usingthe solution as a cathodic cleaner, in which case you can generate hydrogen for embrittlement.

Brian Terryaerospace - Yeovil, Somerset, United Kingdom

November 20, 2013

Q. My initial question may be not clear; sorry about that. We are CLEANING parts, not plating

parts. We just simply clean parts in ultrasound tank with Omegaclean solvent (by Omegasonics).Thanks.

David Ho

- Milford, Connecticut, USA

November 20, 2013

A. For hydrogen embrittlement to occur, generally two factors must be present: (1) a

mechanism for producing hydrogen, and (2) a process that seals the hydrogen into thesubstrate. Since neither of these two factors would appear to be present in your process, onecan reasonable assume that it is hydrogen-embrittlement-free.

Tom Rochester

Plating Systems & Technologies, Inc. Jackson, Michigan, USA

November 21, 2013

Page 17: Hydrogen Embrittlement in Plating

11/27/13 Hydrogen Embrittlement in Plating

www.finishing.com/1200-1399/1216.shtml 17/17

Q. Out of curiousity, is the 'process that seals' required? I always thought that just exposure

such as cathodic cleaning or acid etching was sufficient to pose a risk.

Willie Alexander

- Colorado Springs, Colorado

November 26, 2013

A. Hydrogen generated during cleaning or pickling (or etching) is usually considered "self-

relieving" in that the hydrogen can escape easily. That is why phosphating and mechanicalplating (to name two non-embrittling processes) are considered non-embrittling processes.Parts tested immediately after plating may exhibit transient hydrogen embrittlement, but thisgoes away as the hydrogen escapes at room temperature without baking.

Tom RochesterPlating Systems & Technologies, Inc. Jackson, Michigan, USA

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