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Hydrogen Bakeout

Hydrogen Bakeout

Hydrogen Bakeout

Does anyone know where I can find some good rules of thumb regarding when hydrogen bakeout should be performed when welding to piping that has been in hydrogen service?  Some data regarding hydrogen diffusivity as a function of partial pressure and temperature would be fantastic, but even some general guidelines would be appreciated.

RE: Hydrogen Bakeout

I have never seen anything on this. I have always thought of it as service identifying. I know this doesn't help but if there is any thing on this then I would be interested to!

RE: Hydrogen Bakeout

Good question. We refurbish valves & wellhead equipment that have been in sour service and have some customers who require we conduct a standard stress relief prior to any work plus a post weld stress relief if welding was performed. The result has been the occaisional scrap of material because we've over-tempered it. I look forward to see if anyone can provide you a more definitive answer.

RE: Hydrogen Bakeout


GENERALLY SPEAKING hydrogen embrittlement is not a problem if the steel alloy is HT to, or less than, 160KSI FTU UTS. IF steel alloy is HT to less than 160KSI FTU, then don't worry about it.

IF You are REALLY concerned, perhaps You could do either of the following:

Bake same as for cad-plating hydrogen embrittlement relief [ref ams-qq-a-416]
weld on a valve, then cut-it up for metallurgical sampling and testing.

Regards, Wil Taylor

RE: Hydrogen Bakeout

I have recently read something that is just what you are asking for, but I can't remember where I read it.  However, I do have a book here with a chart regarding "methanization", which causes blistering in steel due to hydrogen diffusion.  It uses curves based on partial pressure of H2 vs. temperature for various steels.  The book is called "Corrosion Control in the Chemical Process Industies" and is available from NiDi (Nickel development institute) at no charge.   "Weldability of Steels" by Stout also has a chart for solubility of Hydrogen in Iron.  I don' think these are exaclty what you are looking for, but if I can remember where I got that other information, I will post it.

G Roberts

RE: Hydrogen Bakeout

why not read NACE MR 01 75. it deals with means to avoid hydrogen embrittlement of various grades of steel in sour service. formulas, charts, and heat treatment; I think it will help.

RE: Hydrogen Bakeout

Why not read NACE MR 01 75 . It deals with means to avoid hydrogen embrittlement of various grades of steels in sour service. It provides formula for H partial pressure, charts and h/t required vs steel grade. I think it will help.

RE: Hydrogen Bakeout

we will be welding 40'lemgths of 20" a53grade b stdwt for a pipeline. what woud be crew size and productivity?

RE: Hydrogen Bakeout

On the subject of Hydrogen embrittlement, I have a question regarding baking HT steel after it has been electroplated with a di-chromate zinc plating.
EN 12329:2000 has been mentioned to me but none of the standards, I have come accross help me deide the baking process necessary, baking time, maximum time to oven post-plating etc.
Anyone any ideas

RE: Hydrogen Bakeout

SAE has three standards that cover this topic quite well:



Ford, GM, and DaimlerChrysler all developed their own internal standards that were the basis for the two USCAR documents.  ASTM also has a number of standards on the subject:


ISO 9588 is the worldwide standard to which ASTM B 850 is the US equivalent.  ISO document can be obtained directly from ISO at http://www.iso.ch or from Global Engineering Documents at http://global.ihs.com/ .

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