Black phosphate treatment for factory bolts
I came across a good process on how to restore bolts to the factory black color and thought I'd share. Here's a list of the things you need :
Phosphoric Etch and prep - Home depot carries it for under $ 20.
2 32 oz. Pirex measuring cups - or any other decent glass beaker.
Electric hotplate - no gas.
Long nose pliers - they might get ruined
Tall skinny glass jar
I started with glass blasted bolts. Put the 32 oz. Pirex measuring cup on the hot plate at low to medium heat. Fill about half way or less with the etch and prep. I only do 4 control arm bolts and 4 nuts at the same time. They bubble in the solution and it turns to foam. Anymore than that and it will foam over fast. I always do this on my garage floor away from everything. It takes about 20 minutes. Fill the second cup with distilled water and the tall jar with acetone. Take 1 bolt out at a time using the pliers. Dip it in the water and then into the acetone. You can use compressed air to dry it or just set it on the paper towels. The acetone dries fast. That's it. If you want it darker you can put it back in the etch and prep. Sometimes it takes 2 rounds to come out nice. If you do too many bolts at once it foams too much and the bolts are in foam instead of liquid.
The article I found said you can clear coat them, but that defeats the purpose in my opinion. I saw a 64 GTO that was unrestrored with only a few thousand miles in perfect condition. All the fender bolts, a arms bolts, control arm bolts etc were this black.