Suspension Finishes

[MJinCO]

I'm going to be building some new front suspension control arms this winter and would like to know how people are finishing them. I'm changing from the original Spitfire upright modified to have a lower ball joint apparently from a '60's Cooper to a bottom 5/8" rod end so will be making some new control arms to fit. The control arms will be 7/8" 4130 tubing with rod ends, my current control arms and some old uprights appear to be Cadmium plated and am curious how newer ones are finished.

[Rick Kirchner]

Vintage car? Nickel. Electroplated if you can get it, electroless if you can't

[MJinCO]

Yes, very vintage 1971 Ocelot, thanks for the info.

[10rmotor]

We used bright nickel plating on our Amac DSR suspension pieces. It seemed pretty durable even after many years of use. One of the nice things about that finish is if you needed to weld on it there were no issues with contamination.

[jrh3]

Hopefully someone will jump in with a discussion of embrittlement.
Electroless, electroplated nickel and cadmium as well as need for post plating baking of mild and higher strength steel.

[Rick Kirchner]

I did not think electroless experienced hydrogen embrittlement.

Regardless, if you do electroplating on racing parts its best to find a plater that does it to mil-spec, and then ask them to follow the process (but you don't really need the certs $$$$)

[Lee Johnson]

Hopefully someone will jump in with a discussion of embrittlement.
Electroless, electroplated nickel and cadmium as well as need for post plating baking of mild and higher strength steel.

Hope it is not too detailed & abstract: the following paper from Fastenal Corp. has some good layman-level info on the topic of hydrogen embrittlement --

https://www.fastenal.com/content/fed...rittlement.pdf

The paper is focused on fasteners, but much of the info also applies to other steel parts. Some excerpts from the paper include--

1) "In general, if the hardness of the fastener is less than 35 HRC [Hardness, Rockwell C-scale], there will probably be little difficulty with hydrogen embrittlement. However, if the fastener has hardness above 40 HRC, problems are more likely to occur."
2) "Coating processes such electroplating can introduce hydrogen during the acid cleaning stage."
3) "If electroplating is still desired, ensure that the plater uses the proper procedures and bakes the fasteners
correctly based on the hardness of the fastener....ASTM F1941 has a hydrogen embrittlement relief requirement for coated fasteners made from steel heat treated to a hardness of HRC 40 or above, case hardened fasteners, and fasteners with captive washers
(SEM screws) made from hardened steel. The exact time and temperature of the bake is not specified, but times between 2 and 24 hours at temperatures between 350 and 450°F are listed as suitable depending on type, size of fastener, geometry and other variables." [Note that these temperatures can be achieved in a kitchen oven, only if SWMBO ("she who must be obeyed") agrees of course!]
4) I've read elsewhere that electroless plating processes directly to the part are less prone to inducing hydrogen embrittlement than electroplating processes, but can't quickly find a reference.
5) A Wikipedia article also mentions the possibility of creating hydrogen embrittlement due to improper welding: "A common case of embrittlement during manufacture is poor arc welding practice, in which hydrogen is released from moisture, such as in the coating of welding electrodes or from damp welding rods.^[22][31] To avoid atomic hydrogen formation in the high temperature plasma of the arc, welding rods have to be perfectly dried in an oven at the appropriate temperature and duration before use. Another way to minimize the formation of hydrogen is to use special low-hydrogen electrodes for welding high-strength steels."
Link ==> https://en.wikipedia.org/wiki/Hydrogen_embrittlement

Lee