CAD Plating and hydrogen embrittlement

I'm going down the path of getting hardware re-plated for my 75 project in CAD. Let's put the sanity of that decision aside so we can focus on my real questions. I've read about hydrogen embrittlement after plating and know you can request your parts to be baked immediately after plating to mitigate the effects. HOWEVER, it does seem that some hydrogen migration happens no matter what and can weaken the fastener. Further the problem is worse with high tensile strength fasteners. And it seems to be cumulative, so subsequent platings make the problem worse. So my questions boil down to what to worry about? If I plan to have the plater bake the parts after plating - is it OK to replate head bolts? Axle Bolts? Disc rotor studs? Cylinder base studs and nuts? etc. How about headsteady or centerstand springs? i.e. what to avoid and what to not worry about?

Also what does the collective hive mind say about removing studs from their current happy resting place. What I mean is, is it a good idea to remove studs (say disc rotor studs or engine case studs)? It's my thinking that disturbing the aluminum threads by twisting these in and out is probably to be avoided. Is this really something to worry about, or should I just pull 'em and plate 'em and not think twice?

Any input very much appreciated. Technical references you can point to might be interesting too!

-- Thanks, David

Cad plating used to be done in cyanide, so there was no actual acid involved. (Except maybe in the cleaning.)
Its also done at a relatively low voltage/current, compared to the mega-amps and temps chrome uses for example.

Some places still do cad plating to aircraft standards, so if you have any concerns run them past them.
Aircraft folks don't like having the wheels fall off, and the certificate the bolts etc come with say they won't.
Aircraft cad is often that yellow-green color though, not the silvery look finish that Nortons used...

Hopethishelpsabit.

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IMO...........Why would someone CAD plate 2nd hand 40 year old nuts bolts that have been torqued up and used and reused... Its real cheap to have them plated by the kilo but for an extra 20% $$ you can buy new !!!!!!!!!!! I dont believe that its likely that each and every nut and bolt will return to the original position.. Always lose some or have leftovers .. then you go buy new that are different....

Dont waste you time and money and just buy new,, I have spent about $250Au on new nuts and bolts and washers with the majority being S/Steel .. If i need 4 i have always brought x 2 times......... So might really only be $200 worth.......

A hundred dollars here and there in a 10k project, WTHell

Have you spoken to your Cad plater regarding your concerns and if so what is his opinion? I'm sure a reputable cad plater
would be able to give you some advice, thats their biz

olChris said:

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IMO...........Why would someone CAD plate 2nd hand 40 year old nuts bolts that have been torqued up and used and reused... Its real cheap to have them plated by the kilo but for an extra 20% $$ you can buy new !!!!!!!!!!! I dont believe that its likely that each and every nut and bolt will return to the original position.. Always lose some or have leftovers .. then you go buy new that are different....

Dont waste you time and money and just buy new,, I have spent about $250Au on new nuts and bolts and washers with the majority being S/Steel .. If i need 4 i have always brought x 2 times......... So might really only be $200 worth.......

A hundred dollars here and there in a 10k project, WTHell

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Well Chris, one reason for keeping the old fasteners, IF they are in good overall condition, is that they tended to be very well made and made out of correctly specified materials.

Many racing based shops take the approach of re-using good original fasteners, I guess the 'form vs function' equation is more skewed to function on the track.

Replacing old ones, for shiny new ones MAY be a downgrade! Unless, of course, you really know what you're buying and / or buy from a proven and reputable source.

Having said all that, on my own current project, I had a mix of old and new/ good and bad fasteners on the bike, so ended up going the shiny new route and bought most from Matt at CNW and am very pleased with the overall quality, especially the engine fasteners.

CAD plating of parts and hardware is common especially on aircraft fasteners. What you need to do is have the CAD platers bake the hardware after they have been plated. Baking boils out the hydrogen gases. You pay extra for the baking process but I think it is worth it. I have talked with some people who would do the baking of the fasteners at home in their oven however, I think that is a bit of a false economy. I knew one guy that had some high stress parts for a North American B25 CAD plated and he literally stood by and watched the guys bake the parts to ensure that those parts had indeed been baked.

Also I assume you want the hardware silver in color. That process would be called CAD 1. If you want a gold color it is CAD 2.

I used to work as a chemist in the aircraft industry, and two other defence areas. In one application we used allen headed cap screws to hold two halves of a solid fuel rocket together.. One day a rocket was stood upright on the deck of a ship for firing, and the head of a screw rolled out onto the deck. That rocket carried a torpedo. The pickling of the screws was changed to anodic alkaline cleaner. And the plating process changed. It had always been cyanide based - became 1/10th plate, bake for 4 hours @130 degrees C, plate to thickness, then bake for 20 hours@130 degrees C.
Even though there is no acid involved in the process, the screws become the cathode, and that is where hydrogen is released. The screws don't usually brake if embrittled, until they have been under tension for a while. High tensile steel is the most susceptible to embrittlement.
It might interest, that there is a guy in South Australia built a W196 Mercedes replica. He used flattened (oval) hydraulic tube on the front suspension, and nickel plated it. The car collapsed onto his garage floor overnight.

If you have hardened parts like most fasteners you must have your plater bake out after plating to industry specifications. I have personally seem fasteners pop that were improperly baked out. Hydrogen embrittlement really exists.

acotrel said:

I used to work as a chemist in the aircraft industry, and two other defence areas. In one application we used allen headed cap screws to hold two halves of a solid fuel rocket together.. One day a rocket was stood upright on the deck of a ship for firing, and the head of a screw rolled out onto the deck. That rocket carried a torpedo. The pickling of the screws was changed to anodic alkaline cleaner. And the plating process changed. It had always been cyanide based - became 1/10th plate, bake for 4 hours @130 degrees C, plate to thickness, then bake for 20 hours@130 degrees C.
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A bit off subject ( but I'm sure I'm not the first to do so on this forum) Was the rocket an Ikara? Reason I ask, my dad worked on the design of its radar system at WRE Salisbury. It was an interesting project and consumed a large chunk of his working life.

acotrel said:

It might interest, that there is a guy in South Australia built a W196 Mercedes replica. He used flattened (oval) hydraulic tube on the front suspension, and nickel plated it. The car collapsed onto his garage floor overnight.

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Something is seriously flawed with that scenario !?
Rickmans for one used nickel plated frames, and don't have any significant problems ?
(Seeleys too ??) (Not that we know how they heat treat them.)

Nickel plating is said to be quite flexible, whereas chrome plate is quite brittle, and can crack if flexed much.
And the cracks then propagate through the base metal.
Although you see chromed frames and seat springs especially, and they survive...

P.S. Frames are satin nickel plated (?), maybe that makes it different ?