I finally got my electroplating setup working. I'm planning to zinc plate many of the original M37 fasteners, as well as a number of other parts.
Here's a typical batch of rusted bolts. My preferred method of de-rusting fasteners is glass bead blasting, as it's gentler than many other blasting abrasives, but still effective, and it leaves a finish that I like. If glass bead blasting cleans up the fastener nicely and there isn't any deep rust or other damage, I'll generally re-use the fastener, but if it's a torque-to-yield fastener, or if the technical manual says to replace it, I will always replace it with a new fastener of the correct type.
For plating, I used the "Copy Cad and Zinc Plating" chemicals and "Yellow Chromate Solution" from Caswell Plating and followed the process and safety instructions in the
Caswell Plating Manual.
From other reading/research, I also decided to bake the parts immediately after plating to help prevent hydrogen embrittlement, which I have heard is especially important for harder steel parts.
Here are a few photos.
Some headlight mounting bolts right after glass bead blasting.
The same bolts in the plating solution:
Baking the bolts right after plating:
The same bolts hanging up to dry after the chromate conversion coating step:
Note: I could have added a 'brightener' from Caswell to the plating solution if I wanted a shinier surface, but I prefer this surface treatment, since my theory is that paint will adhere better to this semi-matte surface than a shiny surface, and since it's a military vehicle restoration, most of the fasteners and other parts will end up being painted.
Here are some headlight retaining rings that needed some attention:
One of the headlight retaining rings after some straightening and bead blasting:
A couple of the headlight retaining rings after zinc plating and a chromate conversion treatment:
WARNING: Be sure to follow all appropriate safety instructions when working with plating chemicals and processes.