Wednesday, April 18, 2012

Back in Black – Oxide, That Is

Being certifiably out of my mind, when I endeavor to do strange and unusual things in my shop, it rarely raises any eyebrows.  However, my latest little foray into the unknown has a few of my car-guy buddies rather enthused.
Specifically, I spent several months complaining about the apparent difficulty and cost associated with getting parts coated in black oxide for corrosion protection and good looks.  It’s not that it can’t be done locally you understand (I’m all about that whenever possible), it’s the entire headache of the experience, from cost, to “down-time” to cost…… get the idea.

So, I set off to research what options were out there to accomplish this type of work on a smaller, more affordable scale at home.  Pretty quickly, I found there are basically two players in the “aftermarket” that offer viable black oxide kits:  The venerable Eastwood Company and Caswell Inc. 

As much as I appreciate the efforts of the Eastwood Company to support our hobby, my personal experience with most of these types of “kits” they offer has been anything but shining.  On the other hand, I have dealt with Caswell for several years on powder coating matters and find everything they offer to be top shelf and have never been disappointed.  With little hesitation, I purchased Caswell’s 1.25 Gallon Black Oxide Kit and waited only a few short days before it was at my door.  This kit was particularly interesting to me based on the fact that it was a “cold” process as opposed to the old standard “hot” process.  This technology was pioneered by the gun industry and the finish is found on countless firearms in almost every conceivable form.

The kit arrived very well packed and was rather surprising in its simplicity.  The instructions were very easy to follow and with a few gallons of distilled water on hand, I was able to get started with my first batch of parts within minutes.

The simple process involved mixing the blackening agent with distilled water in the supplied 1.5 gallon bucket.  Then, as simple as you please, I submerged my freshly blasted pinion support bolts as well as a tapered snap ring installation sleeve I made to help in rebuilding Ford Cobra Mustang rear brake calipers (long story).  I used an old pair of long needle nosed pliers to place and retrieve the parts in the solution with the total submerged time of less than 5 minutes total.

The parts emerged from the solution a wonderful, even and very attractive black oxide finish, ready for sealing.  The protective, penetrating sealant supplied in the kit is an oddly oily dark amber fluid that smells a bit like shellac.  A quick 5-minute bath in the sealant was all that was required and I set the parts to the side for a few days to allow the sealant to penetrate and dry per the instructions.  A quick drying off with a paper towel revealed perfectly uniform and evenly blackened parts with absolutely no headache whatsoever.

Since I have many more small parts I want to finish in black oxide, I expect to get a lot of use from this inexpensive and easy-to-use kit from Caswell.  The packaging allows you to preserve the solution in the bucket it is shipped in and that makes storage between uses quite painless.  So far…….I’m a big fan!
Here is the Caswell black oxide kit ready for use.  The parts in the foreground are my intended victims:  my 9-inch pinion support bolts as well as a tapered snap ring compressor I made for assembling Cobra rear brake calipers.

I was half-way expecting complicated instructions with the kit, but I was pleasantly surprised at their simplicity.
Caswell supplies two cans of their penetrating sealant that is to be applied immediately after the blackening process is completed.

The mixed blackening solution has the appearance of light blue, slightly soapy dishwater with almost no odor at all.

I had to laugh a bit as the solution quickly blackened the pliers I used to retrieve the parts after the prescribed treatment time.

Here are the pinion bolts after about 3 minutes of soak time in the blackening solution.  As you can see, they are already very well coated in black oxide.  I followed the bolts up with the tapered sleeve tool I made and the results were equally impressive.

If you look closely, you can just make out the tapered sleeve at the bottom of the can of sealant.

And here are the parts fresh out of the sealant and ready for the drying phase.  The finish is excellent and once dry, the parts look every bit as nice as any commercial black oxide coating I have seen.


  1. Sven, do you think the sealant will prevent rust? I know my experience with black oxide fasteners from McMaster-Carr has been poor. They look good for a few months then gradually start showing small amounts of rust spotting. Perhaps just another fine product of China? Will be interested in how they hold up. Nice tip with Caswell. Thanks!


  2. RJ,

    In all honesty, I doubt the sealant will prevent rust entirely but I am hoping it will improve durability over standard black oxide. The gun guys say it's better and the finish looks quite nice. It will be interesting to watch.


  3. That process looks a heck of a lot simpler than my "boil them in phosphoric" acid treatment! Great results too. If you wipe them down after removing them from the bath, does the black oxide wipe away? It shouldn't.

    1. Alex,

      It is so simple it makes you feel like it shouldn't work! The finish on the parts was very solid and was basically unaffected by any handling I gave it. Once the sealant is dry and the parts are wiped clean, they look really nice with a very deep black finish. Neat process and super-easy.


    2. Impressive. Caswell does it again. Thanks for the demo Sven.

    3. I will keep monitoring it, but so far it's a winner.