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Parkerizing

In Part I, we presented the simplified process, and discussed the various supplies and equipment. Now let's go into the details of the process.

Cleaning Your Parts

Parkerizing only works on clean plain steel parts. It will not work on stainless steel, brass, or other metals. If your parts have previously been cadmium plated or zinc plated, you will need to remove those in an acid bath. We'll discuss that in a minute. If your parts have been chrome plated or nickel plated, you will need to have a plating shop professionally strip them.

First step is to mechanically clean the parts to get them as clean as you can.

Next you should bead blast them if you have the equipment available. After blasting, wear cotton gloves so your skin doesn't touch the parts, since the natural oil in your skin will interfere with Parkerizing. Use a clean wire wheel on your bench grinder, or a clean toothbrush-like wire brush to get the majority of glass beads and bead dust off the part.

If you don't have bead-blasting equipment, you should use an acid bath. Put on your gloves and safety glasses. Pour the concentrated muriatic acid into an appropriate container, then add your parts. It will remove zinc and cadmium plating within a few seconds. A minute will clean most things down to bare metal. Now remove the parts and put them in another container of cold water. Turn the cold water tap on and let the flowing water rinse away the acid.

Pour the used acid into a plastic milk jug with a small plastic funnel and save it for next time. Pouring it through a stainless steel strainer is a handy way to catch any small parts. When it gets really gunky, carefully pour it into a large amount of cold water, and dispose of it.

Your parts must be squeaky clean. Dirt, grease, even the natural oil in your skin will prevent the Parkerizing process from “taking”. Handle your parts with clean towels or white cotton gloves to avoid contamination.

Hot Water Bath

Before Parkerizing, it's a good idea to put your parts in a hot water (190-200 degree F) bath for 5 minutes to get the parts at the same temperature as the Parkerizing Bath. Otherwise, the cold parts will reduce the temperature of the Parkerizing Bath, reducing its effectiveness. This also opens the pores of the metal so any glass beads / bead dust will fall out, and does a final rinse of any muriatic acid.

This step is optional. It will require another pot and another heat source. You could heat the parts in your barbeque, but that won't get the glass beads/dust out as effectively.

Parkerizing Bath

Put on your gloves and safety glasses. Fill the pot with enough solution to cover the parts and 50% more. Heat it up on your heat source to 190-200 degrees F. Use the cooking thermometer to check the temperature. Keep the lid on to prevent evaporation of the solution.

Drop the parts into the pot. They will immediately start fizzing. After about 5 minutes the fizzing will stop, and the parts will have turned a nice gray color. Some metal will turn a medium gray, some will turn a charcoal gray, some will turn almost black – it depends on the metal composition of the part. 5 minutes should be all that's required.

Remove the parts using your tongs, or stainless steel strainer. You can give them a dip in your hot water bath to rise off the Parkerizing solution. Towel dry.

Cold Water Bath

Don't. The directions that come with most Parkerizing solution are written primarily for gun owners, as they are much more plentiful than antique motorcycle buffs. The directions may tell you to rinse the parts in a cold water bath. Here's where you might want to NOT follow the directions.

Why? Gun owners routinely disassemble, clean, and oil their guns. They don't drive them through puddles or let them sit out in the rain. So gun owners are more concerned with pristine appearance, and less concerned with optimum rust proofing. For motorcycles, we want optimum rust protection. We're doing nuts and bolts that few people will ever examine up close. For motorcycles, skip the cold water bath.

Oil Bath

Many directions tell you to spray the parts with WD-40, or use some proprietary kind of preservative. WD-40 might be great for guns, but for motorcycle parts, motor oil is a better choice. I don't think it matters much whether you use genuine Harley 60 weight or good old 10W-40.

Some people say to use the dirtiest used motor oil you can find. Used oil contains acids formed by the internal combustion process, so clean new oil is a better choice.

It's best to put hot parts in warm motor oil for maximum absorption, although you can put cold parts in cold oil. So, heat a pan or pot of motor oil in your backyard barbeque. Put your dried parts in the oil and let them sit for an hour. Or overnight. Then wipe the oil off and leave them on a towel. The next time you look at them, they will be oily again. They will continue to weep oil for quite some time.

Cleanup

The Parkerizing solution can be reused over and over. It takes quite a while for a large pot of the solution to cool, so to speed things up, plug the drain of your laundry tub, add cold water, and then put your Parkerizing pot in it. When the outside of the pot reaches room temperature, you can transfer the used Parkerizing solution into your HDPE #2 milk jugs.

The solution will have some white sediment in it this won't hurt anything, but it's best to decant the solution and discard the majority of the sediment. You can also use a coffee filter in a funnel to strain out most of the glop. You will lose some solution to evaporation while cooking. You will lose some during decanting. Just add fresh solution to make up for the losses. When you first mix up your solution, mix up two or three times what you'll need on day one, and you'll be have enough to last you for years.

Clean your stainless steel cooking pots with a nylon or stainless steel Scrungie. Don't use steel wool or anything with plain steel in it. Plain steel particles will embed themselves in the stainless, and you'll soon find that your stainless is rusting! If you get a buildup of limescale on the bottom of your pots, try some muriatic acid – it will dissolve the limescale after soaking for 30 minutes or so.

Practice Run

One idea for a practice Parkerizing run would be to buy some plain steel 5/16 and 3/8 fine thread nuts and lockwashers from someone like McMaster-Carr. Or buy zinc-plated ones and acid strip them. Parkerize a bunch of them. If you mess up, well, it's only nuts and lockwashers. Succeed, and now you've got a stock of the most common fasteners used on a Harley.

Notes

The name "Parkerizing" comes from the Parker Rust-Proof Phosphating Company of America, which started business in 1915. Today, “Parkerizing” is a trademark of Henkel Adhesives Technologies, although like “xerox machine” it is used generically. The term “Bonderizing” was used in some of Parker's early patents, but the origin of the term is unknown.

Manganese phosphate and zinc phosphate are similar, but manganese is best as a final finish. Manganese phosphate typically gives a darker color than zinc. Zinc is better for parts that will be painted. You can paint over either kind, but do not do the oil bath if you plan to paint the part. Industrial companies, like Harley, may do the process in large pressure-cookers where the temperature may reach 1000 degrees. This is hard to achieve in the home garage.

 
That's pretty much all there is to Parkerizing. It really is as easy as boiling water.

Back to Part I