Charlie's Shed - Chemical Blacking

 Way back in the dim and distant, when I was rebuilding my SQ4 in fact, I had an incomplete set of engine bolts so the SQ4, like the FH years later, wears stainless steel fasteners everywhere. That incomplete set was chemically blacked, a process which was almost universal for protecting fasteners from corrosion until the 1940's, when Cadmium plating became popular.

Cadmium is pretty toxic, and by the mid 1980's most fasteners were zinc plated - a process very much in use today.

However! Our Model A is not going to be wearing shiny fasteners, which raises a little machining challenge! The issue is, when we are missing fasteners, the ones that are commercially available are either stainless or zinc plated - and will probably not be the right pattern - we don't want nuts with both sides chamfered or bolts with stamped text on the heads! Secondly I don't want to spend hours removing zinc plating, so we will make the missing fasteners on the lathe.

Here's a batch of 1/2" CEI nuts I made earlier:

So here goes. This is the GP Cool Black Metal Blackening Kit from Gateros Plating, and if I recall correctly this is the 1 litre kit.

Here are the instructions:

For the first try I followed Process 2 in the instructions, with 3 minutes in Cool Black solution and drying the Rogard Supreme Seal with the hot air gun. A bit patchy but an online video for another manufacturer's kit suggests that 5 minutes in the alkaline cleaner is required, not the quick dip & wiggle that it got from me.

For the second job, I used Process 1 with two minutes in the Cool Black solution:

Third job: a wash with carb cleaner, 2 minutes in the alkaline cleaner, 2 minutes in the activator, 2 minutes in the cool black, 2 minutes in the oil. Much better:

The ambient temperature here is about 5°C, and I am doing this in an unheated workshop!

I think I'm getting the hang of this now. This is a spacer for the frame stud near the top of the gearbox, and after a dose of carb cleaner and a rub over with a rag and a brush dipped in alkaline cleaner it was unable to pass a water break test. I dipped it in the alkaline cleaner again for 5 minutes after which it successfully passed the test. This was followed by 1 minute in the activator and 2 minutes the cool black - this picture was taken after the first 30 second dip in Rogard: 

This is the finished spacer - which ironically I'm not going to use - it's now had three dips in Rogard and one dip in dewatering oil.

I'm calling that a success.