Do-It-Yourself Phosphating

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Written by Don Stewart | 01 November 2002

If you’ve decided to do a full “nuts-and-bolts” restoration, you’ll eventually face the question: “How do I handle the job of restoring the parkerized parts; i.e., the parts with natural phosphate and oil finish?” You’ll have to decide whether to send them to a jobber, buy reproduction or NOS parts, or do the phosphating yourself. Sending parts to a jobber risks losing small pieces like bolts or screws with special markings on their heads. Buying reproduction parts, especially fasteners, from an outfit like AMK is a good choice but some parts aren’t available. Likewise, the availability of NOS fasteners is unlikely. In the end, you may decide to preserve irreplaceable pieces by phosphating them yourself.

The thought of doing the job yourself may be intimidating but other than the time involved and a relatively minor expense for tools and supplies, it’s quite straightforward. The tables that follow give an overview of what you’ll need and the procedure to use:

Parkerizing Solution

The concentrate is available from:

Palmetto Enterprises

2311A Old Parker Road

Greenville, SC  29609

864-246-3836

There are two concentrates: one is for black parts and the other is for dark gray parts. Mustang parts are dark gray.

Tools and Supplies

  • Stainless steel tank or kettle big enough to handle the largest piece(s). Pyrex and porcelain enameled containers can also be used but they’re easy to chip or break.
  • Small stainless steel container for bolts and screws.
  • Hot plate or other controllable heat source.
  • Thermometer (like a cake thermometer) good for at least 200o Fahrenheit.
  • Tongs at least 8-inches long.
  • Naval Jelly.
  • WD-40 in both bulk and spray.
  • Small open-top container to hold bulk WD-40.
  • Gun oil.
  • Safety glasses

Procedure for Do-It-Yourself Phosphating

  • Put your safety glasses on.
  • Remove oil and grease from the parts.
  • Media blast each piece to remove the old finish plus any paint or corrosion.
  • Coat (etch) each part with Naval Jelly following directions on the container.
  • Assemble the tools: hot plate, thermometer, tank(s), tongs, WD-40, gun oil.
  • If you’re doing small parts such as nuts and bolts, pour some WD-40 into a small container. The container should be big enough to allow you to submerge the parts in the WD-40.
  • Mix the Parkerizing concentrate with distilled water (typically, one ounce to one quart water). Mix enough solution to completely cover the parts when they’re in the kettle.
  • Preheat the solution to between 160o and 180o Fahrenheit. Preheat to near 200o if you’re doing large parts because the temperature will drop when large pieces are put in the tank.
  • Thoroughly wash the Naval Jelly from the parts. Don’t worry about drying them because they’re going immediately into the phosphating solution.
  • Most parts can be placed right into the hot solution but springs (e.g.: hood springs) and assemblies that contain springs (e.g.: hood latches) should be submerged in the solution and then removed after about a second. Put them back into the solution after a second or two and then remove them again after two seconds. Repeat this cycle five or six times and with each cycle, increase the length of time you leave the spring submerged. Finally, leave the spring in the solution. What you’re doing is heating the spring slowly to reduce the risk of thermal-shock-failure caused by a sudden change in temperature. See below for more about springs.
  • Turn the parts once each minute so those surfaces resting against the kettle get better exposure to the solution.
  • When the parts are in the hot solution, they will fizz or bubble during the chemical reaction. When the fizzing stops, the process is complete. Remove each part from the kettle and before it can dry, immediately spray it with WD-40 to prevent the formation of white streaks. Don’t try to spray the nuts and bolts. Drop them into the small container of WD-40.
  • Lay the parts on a clean board to drain excess WD-40.  A couple of hours later (or the next day, if it’s more convenient) lightly but completely coat the parts with gun oil.
  • The phosphating solution can be used again so you may want to save it in a clean plastic container. Filter it through a coffee filter to remove the white precipitate that formed during the process and then save it for future use.

Some springs have coils that touch each other when they’re in a relaxed state (e.g.: hood springs). For complete Parkerizing, that type of spring needs to be stretched so the coils aren’t in contact. A jacking screw can be used to hold the spring open slightly or it can be left on its device to keep it open. A downside of leaving a spring on its device is that the device can’t be opened and closed with the spring in place. As a result, segments of the device may have a differential appearance after phosphating.