Home-Brew Parkerizing

Rusted Nuts courtesy IronWorks May/June 2012

STORY AND PHOTOS BY FREDERICK FORTUNE

Home-brew Parkerizing

Achieving the proper patina takes patience and practice

 

Parkerizing is a method of protecting a 

steel surface from corrosion and increasing

its resistance to wear through the application

of a chemical conversion coating.

It was perfected in the U.S. around the

turn of the century and primarily used for

arms and armaments in the military because

of its durability, part-to-part lubrication

qualities and its resultant ability to

stand up to adverse climate conditions.

What it also does is provide a dark,

beautiful, protective surface for small

parts that rivals the weather resistance of

more expensive plating or coating techniques

such as cad plating and anodizing.

Many early motorcycle components were

Parkerized as an inexpensive alternate to

nickel, cadmium or later chrome plating.

Unfortunately the process cannot be used

on non-ferrous metals such as aluminum,

brass, or copper. Nor can it be applied to

steels containing a large amount of nickel,

or to stainless steel or chrome. Everything

else is fair game.

You need a number of things to do homebrew

Parkerizing, but only 4 ingredients.

1. Pure Phosphoric Acid (85% Solution),

the active ingredient in rust removers,

usually procured at a chemical

supply house. A 500ml container costs

$35-$50.

2. Powdered Manganese Dioxide (a

very dense and heavy dark gray to black

mineral powder) also available at any

chemical supply house.

3. Distilled water (I use tap water, but

the distilled supposedly gives more consistent

results).

4 A biscuit of fine steel wool 000 or

0000...don’t use soap pads or Brillo™ pads!

I do this on a portable electric heating

element using a one-gallon porcelain coated

metal cooker. I’m told a Pyrex bowl

would work better but they are expensive

and breakable. Uncoated metal pots apparently

won’t work as well (if at all). You

will also need a thermometer to gauge the

water temperature. While you’re picking

up the chemicals, the same supply house

should have those inexpensive 12” long lab

thermometers.

Proceed as follows:

1. Use one whiskey jigger of Phosphoric

Acid per gallon of water. ALWAYS add

the acid to the water, and it is best done

by pouring it down a glass rod.

2. Add one whiskey jigger of the powdered

Manganese Dioxide per gallon of

water to the solution.

3. Bring the solution to an extremely

slow rolling boil. Best results are at or just

under the boiling point.

4. Now add your biscuit of steel wool.

The steel wool will bubble and froth as it

slowly dissolves. If your pot is too full of

water, it may bubble over the sides.

Critical: The part(s) to be Parkerized

should be totally “de-greased” and wire

brushed, sand or bead blasted prior to finishing

depending on the texture you desire

on the finished part. Once you have

cleaned the part, you should handle it with

gloves, never greasy hands, and store it

wrapped in clean paper towels awaiting

the Parker bath. Any grease or “patina” on

the parts or wire will cause a variation in

color...the parts will come out streaked

and/or spotted. Be aware, too, that high

carbon or special alloy steels will not

“take” evenly. The only way to tell is to try.

Place a wooden stick across the top of

the pot and suspend the parts in the solution

using steel or iron wire. DO NOT use

painted coat hangers or any wire with

grease on it! I’ve also just carefully plunked

them in and stirred them around as they

bubble with similar results.

The parts should be totally immersed

in the solution, knowing that anywhere

the wire touches the part or the part

rests against the container will not become

coated or may take a different

tone. If you can’t cover them completely,

turn them over continuously or, with an

old squeeze baster, baste them like a

turkey.

I usually let the part remain in the solution

for a total of 30 minutes (shorter

times results in a lighter color, longer =

darker). If you didn’t suspend the part on

wire, gently fish it out with clean pliers or

wooden tongs. When you withdraw the

part, immediately rinse it in hot running

water to remove the solution. If you use

extremely hot water the already heated

part will dry itself. Let it dry, getting cool

enough to touch, on some clean paper

towels.

The next part is magic. You can do it

minutes or, as far as I know, hours later

but I’ve been too impatient to wait. Having

the part warm as possible is best because

things contract when they cool.

Soak a clean rag in any type of clean

motor oil and apply to the part, working

the oil into the dark grey coating. Watch

as the part takes on a deep, lustrous

charcoal black color. Let it rest and completely

cool down. When totally cool, take

another clean rag and completely wipe

down the part. A microscopic film of oil

will remain embedded in the coating making

the part virtually waterproof and rust

resistant. Bolts and nuts will stand up to

gentle wrenching without scratching,

though they will scratch if roughly treated.

If scratched, sometimes a swipe of

oil will heal the wound.

For more on the history and science of

Parkerizing, visit here:

http://en.wikipedia.org/wiki/Parkerizing

Several caveats:

1. Always be careful of any sort of acid,

even such an innocuous one as phosphoric.

I never deliberately inhale the fumes although

there is no great odor to the

process that I can tell. Just use common

sense, wear gloves and eye protection anytime

you are playing around with chemicals.

2. Be very careful not to cause any

splashes with the boiling solution.

3. Prepare your area and your parts

before hand, don’t try to do this on the

spur of the moment.

4. Once you have allowed the solution

to cool, you are done! Re-heating simply

doesn’t work. Have everything that you

want to Parkerize ready to go when you

fire up the solution. You can keep Parkerizing

as long as the solution is hot, but for

some reason allowing it to get cold kills it

...you’ve have to brew up a new solution

and start over from scratch.

5. If the surface is mottled, uneven or

spotty it wasn’t clean enough. You must

start over with clean, raw steel, wire

brushed and/or sandblasted...no rust,

paint or oil film.

Use at your own risk. Your mileage may

vary.