Hydrogen Embrittlement

[Greg L.]

Do unannealed cad/zinc plated parts initiate cracks within days of being plated, or just as they are being torqued?

I had thought that there were two ways to eliminate the hydrogen in the metal...

-bake the parts at a temp of____? for ____?minutes/hours.

or

-let the parts sit for a few months so that the hydrogen can work it's way back out on it's own.

Thanks.

Greg Linton
#45455

[David S.]

Re: Hydrogen Embrittlement

It really depends on the base material and strength. High strengths steels should be bakes at 375 degrees F for 24 hours within four hours of plating to prevent atomic hydrogen from combining and forming molecular hydrogen. The plating process causes atomic hydrogen to migrate into very small areas (intergranular/grain boundaries)and then combine into molecular hydrogen which is much larger causing the material to exceed its ultimate tensile strength. The post plating bake times and temperatures vary depending upon the relative strength (hardness)of the base material.

The atomic hydrogen will not work its way out on its own. It must be removed before it becomes molecular. Once this happens there is nothing you can do.

I can provide more detail if desired.

Dave

[David S.]

Re: Hydrogen Embrittlement

It really depends on the base material and strength. High strengths steels should be bakes at 375 degrees F for 24 hours within four hours of plating to prevent atomic hydrogen from combining and forming molecular hydrogen. The plating process causes atomic hydrogen to migrate into very small areas (intergranular/grain boundaries)and then combine into molecular hydrogen which is much larger causing the material to exceed its ultimate tensile strength. The post plating bake times and temperatures vary depending upon the relative strength (hardness)of the base material.

The atomic hydrogen will not work its way out on its own. It must be removed before it becomes molecular. Once this happens there is nothing you can do.

I can provide more detail if desired.

Dave

[Phil P.]

Re: Hydrogen Embrittlement

i agree with dave as i've had bolts zinc'd and have had them pop off like a weak 22 shot---also if you have an assembly with a spring in it you will need to do the heat treat or the spring will fail---my 2 cents and lost $ on experience---good luck---phil

[Phil P.]

Re: Hydrogen Embrittlement

i agree with dave as i've had bolts zinc'd and have had them pop off like a weak 22 shot---also if you have an assembly with a spring in it you will need to do the heat treat or the spring will fail---my 2 cents and lost $ on experience---good luck---phil

[Greg L.]

Re: Hydrogen Embrittlement

Thanks guys. So basically the few suspension bolts that I plated myself with my Caswell kit are only good for display now? They look dang good but I probably shouldn't use them now should I?

Dave would you happen to know what the temps and times for annealing some of the more critical suspension fasteners would be?

[Greg L.]

Re: Hydrogen Embrittlement

Thanks guys. So basically the few suspension bolts that I plated myself with my Caswell kit are only good for display now? They look dang good but I probably shouldn't use them now should I?

Dave would you happen to know what the temps and times for annealing some of the more critical suspension fasteners would be?

[Joe L.]

Re: Hydrogen Embrittlement

Greg-----

I would absolutely NOT RECOMMEND messing around with trying to anneal home-plated fasteners that serve CRITICAL SUSPENSION, STEERING, OR BRAKING systems. It's not worth it for fasteners that have very strong safety implications. For these fasteners, if you have any doubt WHATSOEVER regarding the condition of fasteners, either because of home-plating or for any other reason, replace them with NEW, HIGH QUALITY fasteners. Forget about headmarkings and other nuances of configuration.

If you want to take a chance with non-critical fasteners (which are actually the majority of fasteners on the car), go ahead. It's no big deal.

[Joe L.]

Re: Hydrogen Embrittlement

Greg-----

I would absolutely NOT RECOMMEND messing around with trying to anneal home-plated fasteners that serve CRITICAL SUSPENSION, STEERING, OR BRAKING systems. It's not worth it for fasteners that have very strong safety implications. For these fasteners, if you have any doubt WHATSOEVER regarding the condition of fasteners, either because of home-plating or for any other reason, replace them with NEW, HIGH QUALITY fasteners. Forget about headmarkings and other nuances of configuration.

If you want to take a chance with non-critical fasteners (which are actually the majority of fasteners on the car), go ahead. It's no big deal.

[Terry M.]

+1 *NM*

[Terry M.]

+1 *NM*

[Greg L.]

Re: Hydrogen Embrittlement

Okay I'll take your advice and replace all those critical fasteners because I'd hate to lose it all over $50 worth of hardware.

On another note though, is there any way to detect hydrogen embrittlement to see if a part is affected or not? We have a very good NDT guy that comes around work now and then and he does it all like fluorescent penetrant, eddy current and x-ray and I'm just wondering if any of these methods will pick out the cracks?

As far as repro hardware goes how can I know if they have been properly annealed? I was thinking of going with some Paragon bolts because they are the only ones that seem to have correct head markings and they are listed as grade 5 or 8 as applicable.

[Greg L.]

Re: Hydrogen Embrittlement

Okay I'll take your advice and replace all those critical fasteners because I'd hate to lose it all over $50 worth of hardware.

On another note though, is there any way to detect hydrogen embrittlement to see if a part is affected or not? We have a very good NDT guy that comes around work now and then and he does it all like fluorescent penetrant, eddy current and x-ray and I'm just wondering if any of these methods will pick out the cracks?

As far as repro hardware goes how can I know if they have been properly annealed? I was thinking of going with some Paragon bolts because they are the only ones that seem to have correct head markings and they are listed as grade 5 or 8 as applicable.

[Mark #28455]

they're made at the factory

The "repro" bolts still come from a major hardware manufacturing facility, likely the same original supplier if still in business. For example, if you want "TR" head markings, you contact that company and agree to buy about 1000# of bolts - each in 100# quantities - or whatever "small" volume they're willing to sell. So, there's really no worry about the quality - likely no better or worse than anybody elses grade 5 or 8 bolt.

Mark

[Mark #28455]

they're made at the factory

The "repro" bolts still come from a major hardware manufacturing facility, likely the same original supplier if still in business. For example, if you want "TR" head markings, you contact that company and agree to buy about 1000# of bolts - each in 100# quantities - or whatever "small" volume they're willing to sell. So, there's really no worry about the quality - likely no better or worse than anybody elses grade 5 or 8 bolt.

Mark