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topic 37638

Hydrogen Embrittlement in 4140 Steel

A discussion started in 2005 but continuing through 2019


Q. I'm designing a plating mechanism on 4140 steel. The steel will be used in extreme marine environment (200 °C, 30,000 psi). There is a lot of corrosion and thus has to be plated. We've used nickel plating before, and rather than passing electricity, we've opted to use electroless nickel plating. But the plating has posed a new problem. After plating the steel, we'll have to account for hydrogen embrittlement also. I don't think heat treating the steel before and after the plating (ASTM B849-02 [link by ed. to spec at TechStreet]-94 and ASTM B850-98 [link by ed. to spec at TechStreet]-94) would be really practical in this case, but I am ready to do it if it makes the embrittlement less severe. Are there any other ways to reduce hydrogen embrittlement? Also, I'll have to make sure there is electric conductivity after I make the steel surface corrosion resistant. Any help?

Prabesh Lohani
Brigham Young University - Provo, UT, USA


A. Hydrogen embrittlement relief is only required if the steel's strength exceeds 1000 MPa (approx 31 HRC). What is the strength of your part.

There is no alternative to embrittlement relief for high strength steels.

Ron Duncan

Ron Duncan
- LaVergne, Tennessee
It is our sad duty to note Ron's passing on Dec. 15, 2006. A brief obituary opens Episode 13 of our Podcast.


A. Prabesh, in the aerospace industry we use AMS2759/9 [link by ed. to spec at TechStreet] for baking after plating, and it calls out 23 hours at 375 °F within 4 hours of electroless plating. That's not far from the callout in ASTM B850. Current revision of B850 is 1998, by the way, re-approved 2004. Current rev of B849 is 2002.

lee gearhart
Lee Gearhart


Q. Hi, the steel I'm using has 31 to 35 HRC. I'll also have to look for the revised edition of the standard I'm using. Do you think I should use the AMS 2759/9 standard for baking instead?

Prabesh Lohani [returning]
BYU - Provo, UT


Q. Hi, this is a build-up question. I am doing electroless nickel plating with 4140 and 4130 steel samples that have 31~35 HRC. The hydrogen embrittlement testing I'm doing is according to ASTM ASTM F519-17A [link by ed. to spec at TechStreet] -05. This spec. calls for 51-53 HRC samples, but the material I am using is very different from this. Is there any way I can use my own samples (that have a relatively low hardness) to be tested for hydrogen embrittlement? Any help would be greatly appreciated. Thank you.

Prabesh Lohani [returning]
Brigham Young University - Provo, UT, USA


A. The preparation may be a large part of the hydrogen introduction. Acid treatments will cause embrittlement. One suggestion is to use Citric acid, with the pH adjusted to 3.8 using ammonia ( and an anti mold additive)instead of mineral acid. (after alkaline cleaning of course)Heat treat the electroless nickel plated item by first ramping the temperature up slowly over a few hours before reaching the target temperature per specification as suggested by others. Note that there are no crystal boundaries for the Hydrogen to exit, Thus the reason for slow ramp up of temperature. Rapid heating can rupture the bond between the basis metal and EN. A low pH sulfamate nickel strike although, it also embrittles, produces less hydrogen than a Woods nickel strike, thus less hydrogen to remove by baking.

don baudrand
Don Baudrand
Consultant - Poulsbo, Washington

(Don is co-author of the
book "Plating on Plastics")

sidebar2 2006

Is there a way to test electroless nickel plating adhesion on a 4140 steel substrate? I've been using an eddy current plating thickness detector and its giving random results, so I want to use an adhesion test for the plating. Any help would be greatly appreciated. Thank you,

Prabesh Lohani [returning]
- Provo, Utah, USA

November 4, 2011

A. I suggest to read ASTM B571 [link by ed. to spec at TechStreet]
This practice covers simple, qualitative tests for evaluating the adhesion of metallic coatings on various substances

Eduardo Cambiasso
- Buenos Aires, Argentina

February 8, 2019

Q. Hello all, I am facing problem of hydrogen embrittlement in spring plate subjected under 3025 lbs load. Parts are gets cracked while load condition.
Currently we are using C-80 spring steel material grade after 8 hrs hydrogen de embrittlement process @210-220 degree C.

Can I use SAE 4140 as replacement to C80/EN42J grade to achieve no cracks at 3025 LBS load.

Abhishek kashid
Vishay - Mumbai, Maharashtra, India

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