Crank pulley bolts are S2, phosphated and oiled (gray - black). See amkproducts.com, page 4 of their catalog for Finish Codes, bottom of page. Also see page 101, item B-11605 at bottom center of page, "Chrysler Crankshaft Pulley". This is actually a "hex machine screw" with captive conical washer, not a "hex bolt". Bolts are flush on top without captive washers, and machine screws are indented on top.
Phosphating or Parkerizing is the gun black coating on most military weapons and lots of tools and parts since before WWI.
You can paint bolts with a gun black color and bake in an oven, but they won't be correct or original looking.
Or you can degrease with dish soap and tooth brush, pickle in vinegar for a few half days (check rust removal progress every 8 - 12 hours). Physical rust removal with light scraping and wire brushing is better than depending on just chemical removal. Do a final soapy wash with a toothbrush and a rifle barrel brush on female threads, thoroughly wire brush by hand, and set aside. When ready to phosphate with gun hobbyist's solution available on the www, do one more pickle and wire brushing, spray with oven cleaner, rinse in hot water, then follow the solution directions using a stainless pot on a camp stove outdoors. To prevent the 200 deg or so solution from boiling, use a double broiler method, a pan of water under the stainless pot.
Go to
http://www.caswellplating.com/kits/black.htm for a room temperature solution. Maybe this is better than the hot method. I intend to try this soon.
It's important for the parts to be absolutely clean before Parkerizing; i.e., any kind of rust removal product that leaves a residue probably will inhibit the phosphating process. Bead blasting or sand blasting may damage the finish. Vinegar pickle, wire brushing, oven cleaner, and hot water rinse leaves the fasteners squeaky clean for the phosphating process. See photo.
