How to Parkerize Motorcycle Parts at Home
If you have ever looked closely at the fasteners on an old Harley-Davidson, you have probably noticed that many of them are dark gray or black. That finish is not just age or weathering. It was intentionally used to help protect steel parts from corrosion. The process is called parkerizing, and it is an electrochemical phosphate conversion process using either a zinc or manganese base.
Even though that sounds complicated, parkerizing small motorcycle parts at home is fairly simple with the right supplies, careful surface prep, and a little common sense. This article shows the original process I used to parkerize vintage motorcycle hardware and small restoration parts.
For more hands-on fabrication and restoration articles, see the Vintage Tech section.
Because the parts shown here include small front end hardware, this process also pairs naturally with the 1933 Harley-Davidson VL springer front end rebuild.
Supplies Needed for Parkerizing Motorcycle Parts
Here is the basic shopping list I used for this home parkerizing setup:
- Hot plate
- Thermometer
- 8-quart stainless steel stock pot
- Stainless steel wire
- 2 gallons of distilled water
- Manganese parkerizing solution
I purchased manganese parkerizing solution online from Brownells, but you can also find it at well-stocked sporting goods stores since it is commonly used to refinish firearms.
Safety Notes Before You Start
Parkerizing involves hot liquid, chemical solution, solvents, and freshly cleaned steel parts. Work in a well-ventilated area, use gloves and eye protection, and do not use cooking equipment that will ever return to food service. Keep solvents and chemicals away from flame, sparks, children, and pets.
Read and follow the directions supplied with your parkerizing solution. This article documents what worked for my small parts, but the manufacturer’s instructions should always be treated as the primary safety reference.
Cleaning and Surface Preparation
The first step in the process is to clean the parts you want to parkerize. It is very important that the surface is free of dirt and oil. I used a two-step process starting with blasting the parts with glass beads followed by a wash down with lacquer thinner.
Once the parts were cleaned, I put them in the oven at 200 degrees to dry and warm up before parkerizing.
Mixing the Parkerizing Solution
While the parts were warming in the oven, I mixed the parkerizing solution with distilled water in the stock pot. Make sure you add the parkerizing solution first and then pour in the distilled water second.
The directions called for one gallon of distilled water per 14 ounces of parkerizing solution. Since the parkerizing solution came in a 16-ounce bottle, I found it easier to mix the entire contents of the bottle with 146 ounces of distilled water.
Heating the Solution and Suspending the Parts
Next, heat the solution to 195 degrees using the hot plate. By the time the solution reaches 195 degrees, the parts should have reached a similar temperature in the oven. Using stainless steel wire, suspend the parts one at a time in the solution.
Watching the Parkerizing Reaction
The parts will begin to bubble as soon as they are submerged and will continue to do so until the process is complete. I mostly did small parts, so the process only took a few minutes for each part. When the bubbling is complete, remove the part and rinse it with distilled water.
Oil Bath, Black Oxide, or Paint?
After rinsing, you have a few choices. The first is to impregnate the parts with oil by submerging them in an oil bath. This is the most common practice and what I did.
If you want your parts to be really dark, you can also go right from the distilled water rinse to a dip in black oxide solution. Painting the parts is a third option, but make sure to skip the oiling if you plan to paint them.
Finished Parkerized Parts
Here are the results after the parts were pulled from the oil bath. Overall, I would say they are not quite as dark as what you would expect from a professional parkerizing job, but considering the whole process took less than an hour, it was worth a try.
The parkerizing solution is reusable, so I can always give the parts another dip if they start to rust.
