I bought the black oxide kit from Caswell Plating several years back and have been playing with it from time to time. The results have been mixed up to now. I think I finally got it right this time. I had some rear hubs and stubs that need the treatment so I got after it. I bead blasted, wire wheeled and cleaned with lacquer thinner to remove everything that might cause a problem. Parts were dipped and put in reverse osmosis water to remove solution three times. I polished the parts with 00 steel wool between each dipping(optional step in the instructions). Parts were then given the sealing oil treatment with an additional step not mentioned. After parts were dipped in the sealing oil, I took a heat gun and brought the parts up to about 150 degrees. This let the oil bake into the metal. I am very pleased with the results. I am going to clear coat the exposed areas with one coat of high temp clear brake caliper just for extra protection. Maybe a little over the top for parts that won't be seen but I know they have been done right. Judge for yourself.

What is the sealing oil you mention?

The sealing oil comes in the kit from Caswell.

how corrosion resistant is this coating? can the sealing oil be washed off?

Looks nice

From my research, this is a just an aesthetic finish because it's a cold process. The hot bath black oxide coatings do offer some corrosion protection, but the parts are soaked in a 285 degree bath during the process.

But they still look great and the clear coat will offer some protection.

I used black oxide nuts and bolts on my truck. They were orange and rusted solid within 6 months. The black oxide provided no corrosion protection.

Zach

kind of thought so, the rust that is, I have rattle canned some of mine with black paint over the years, holds up pretty well.

does the treatment on the gear portion make it hard to fit together, or are you planning to remove that prior to installation?

Rich

Parts just drop right in. No fitment problem. I am in hopes I got the process right this time. This cold process is what they say is the same process gun manufacturers use. I have no way of knowing if that is a true statement but that is the opening line of the information on Caswell's page

Those do look nice!

I thought that the secret sealing oil in the cold black oxide processes is a common product. I had read that it has a 40 in the name and was once called water displacement.


So, these parts were done with the Caswell Black Oxide kit? I wondered originally if this was the zinc blackener that they sell to go with their zinc plating kit.

I have used my zinc plating kit that I originally bought from them. I used that as a starter. I then bought a real rectifier and added to the kit they sold.

Black Oxide will not stop rust. I use this on some parts I have made for me. It looks nice and gives a finish that will hold oil better than a plain finish. This will stop the rust nut only while the oil remains on the surface