Building a Hybrid Yugoslav M70B1 from a Stub with Screws

January 20, 2012 By George Spafford

George Spafford is building a replica of the Yugo M70B rifle using a stub parts kit. A new installment will appear here every Friday

Parkerizing - Part 2

To Parkerize, you need an abrasive blaster, stainless steel tank, heat source and then either a commercial Parkerizing solution or it's even something you can make yourself quite easily. The blue container is used to store the mixture for future use.

A perfectly acceptable Parkerizing solution can be prepared at home with readily available ingredients. I recommend doing this outside on a camp stove or something like that. You do not want to do it inside because of the fumes that will cause all the steel to rust!

The recipe is as follows:

* 2 gallons of distilled water

* 2 "biscuits" of clean 0000 steel wool

* 1 cup of Klean Strip brand Phosphoric Prep & Etch (or other phosphoric acid etching solution around 35-45% concentrate per the Prep & Etch MSDS sheet)

* 6 rounded tablespoons of manganese dioxide (available at pottery supply stores or eBay, which is where I bought mine)

To mix the solution and treat my parts, I have a 6x6x40-inch stainless steel Parkerizing tank I bought off eBay from StainlessSteelCreations1 for approximately $120. The tank is heavily made and has a bung on one end so you can drain the solution into a plastic container for future re-use.

I do my Parkerizing in my driveway to avoid fumes causing corrosion in my shop. My heating system is an old Coleman camp stove running their tried and true liquid white gas but you can use any heating source you like. I get it prepped and heating up with the tank on top. I then add the water first and then the acid. Always add acid to water — never the other way around.

As the solution is warming up, I shred the steel wool, add it to the liquid with the manganese dioxide and gently stir occasionally. The acid will start breaking down the steel wool and "season" the solution. You want the solution to be at 190 degrees. I use a stainless candy thermometer that clips on the inside edge of the tank to keep track and adjust the flame on the stove accordingly.

I get other things done while the solution ages. Once the shredded steel wool has dissolved, I suspend the parts in the tank using stainless wire. With the above formula, it takes about 30-40 minutes to get a real good Parkerized surface. If the bubbling stops sooner, your parts are done and you can pull them out.

The surfaces are Parkerized at this point. The barreled action was lowered into the solution using the stainless steel wire you see here. The front rubber plug has already been removed. The next step is to quickly rinse the action to remove the solution.

As soon as you pull them out, flush them with water thoroughly to remove the acid and stop the reaction. Then spray with WD40 to displace the water. I then apply Ballistol, or whatever oil I have handy, to prevent rust unless I am immediately going to apply the finish. Some guys stop with the Parkerizing because the Manganese Phosphate creates a nice very dark gray finish and they just rub in oil. That is definitely one approach.

If there are any problems with the Parkerizing, such as inconsistent coloring/conversion, odds are the surface wasn't sufficiently clean or you didn't leave it in long enough. You can re-blast that area and put the part back into the Parkerizing solution. I have found this formula very easy to work with as long as the parts are thoroughly prepped beforehand.

At this point, the parts are Parkerized! It really is that simple. I use a plastic blue Kerosene-type five gallon container to store my liquid for future use. The precipitate is considered hazardous waste. You can pour the liquid through a coffee filter and catch the precipitate. Allow it to dry and dispose of it according to regulations in your area.