Oct 2, 2014

DIY - Homemade Parkerizing Solution - How To Etch a Knife

In this video I share my homemade parkerizing recipe, which will put a dark manganese phosphate coating onto steel, providing a protective metal finish. It is similar to solutions sold by some major sporting goods retailers for a fraction of the price.

Parkerizing is very much like rusting a piece of metal except that the acidic corrosion process, if done correctly, leaves a more durable phosphate coating/layer on the steel that can be impregnated with oil. The oil will then protect the steel from rust and other types of corrosion. This is the intended purpose of the parkerizing process.

Safety first. Use rubber gloves and safety glasses in a well ventilated area when handling chemicals. Although phosphoric acid may be considered mild compared to other acids, it can still burn your skin, eyes, lungs and clothing. It will also stain your skin yellow and strip off a layer of most metal surfaces it comes in contact with. Use caution and be sure to never bring any of your ingredients to a full boil.

Parkerizing can get messy, if you can do the process outside, you will be better off.

Results may vary depending on preparation, solution, steel, ingredients and many other factors. We recommend testing for desirable results on a non-precious item first. Practice makes perfect.

Parkerizing can be re-done but the changes are permanent. Although parkerizing is an effective way to coat firearms, knives and other steel parts, it may change the function of such steel parts. Parkerizing strips off a layer of metal from the steel parts and turns it into a phosphate coating. This changes the actual physical size and/or dimensions as well as the texture and chemical structure of the outer layer of the steel parts. Additionally, parkerizing may ruin springs, fine threads and factory tolerances on steel parts. Heed this warning before you start parkerizing anything expensive or anything that cannot be replaced.

Sandblasting will also take a small layer of metal from steel parts and cannot be undone. Don't bead-blast your metal parts. This dings metal and will leave a noticeable texture (unless you prefer that). Black aluminum oxide abrasive is really cheap and works great. I used a homemade blasting cabinet with a $15 sprayer from Harbor Freight. Be sure to take all safety precautions as getting sandblasting dust in the air is hell in a hand basket and can cause disease in the lungs if inhaled.

Distilled Water (several gallons): Use only distilled water for impurities in tap water can cause staining on your parts and inhibit the chemical reaction.

Klean Strip Phosphoric Prep & Etch (1 gallon): Phosphoric acid is the active ingredient in parkerizing. Prep & Etch contains enough phosphoric acid to create an effective parkerizing solution. Prep & Etch itself is typically used to etch metal prior to priming/painting. Concentrated phosphoric acid can also be substituted.

000 or 0000 Steel Wool Pad (1): Steel wool comes oiled from the factory to prevent it from rusting. Before using the pad, you will need to degrease it by washing off the oil with dish soap or other cleaners (i.e., acetone and lacquer thinner). I prefer dish soap.

Manganese Dioxide from (2) D-Cell Alkaline Batteries: You will need to retrieve manganese dioxide or "the black stuff" out of two D-cell alkaline batteries, which should be enough for one batch (about 2 gallons) of parkerizing solution. You will need to use a hack saw to cut through the outer metallic case of the batteries. Then, separate the manganese dioxide from the white inner core.

Stainless Steel Pots or Containers: Use only stainless steel containers to heat up the parkerizing solution because stainless steel will not corrode from the acid in the solution. Aluminum, steel, cast iron and copper will corrode from phosphoric acid and you risk running a leak and/or destroying your pots or containers. Don't let your wife catch you using her stainless steel pots and pans. She will not be happy about  it! 

Gun Oil: Gun oils that contain PTFE (Teflon) work well and provide long lasting protection on a parkerized surface. But, in all honesty, any oil that will effectively displace water should work to prevent rusting. You will want to make sure that the oil (most common is gun oil) you use has molecules that are small enough to soak into the parkerizing surface.

Surface Preparation
You will need to remove all dirt, grease and oil from the surface of your steel/parts. Lacquer thinner and a rag works great.

You will need to get your steel down to bare metal for the parkerizing solution to work properly and uniformly. The easiest and best way to do this is to sandblast your parts with black aluminum oxide abrasive. This will create a smooth, even and bare metal finish. Additionally, sandblasting will remove any remaining residue from the surface of the steel, leaving it very clean for the parkerizing bath. An alternative method involves sanding the metal surfaces by hand with sandpaper. However, getting a smooth, even finish using this method can be very difficult.

Keep in mind that once steel has been sandblasted it may flash, rust or corrode from moisture in the air within minutes. Therefore, it is recommended that you have the parkerizing solution ready so that your steel parts can be placed in it immediately after they are sandblasted.

Lastly, and perhaps most importantly, do not touch your metal parts with your hands/fingers or anything else after sandblasting. Only handle them with a clean, dry piece of cloth. Your fingers have salts on them that will corrode the bare steel after you've touched it.

Mixing the Parkerizing Solution
To create the parkerizing solution, you will need to mix 1-2 cups of Klean Strip Phosphoric Prep & Etch per gallon of distilled water used.  Then, add 1-2 D-cell batteries worth of manganese dioxide per gallon of solution. The amount of amount of solution will depend on how much water is needed to completely submerge your parts.

Once mixed you may begin heating the solution over the stove.  Slowly heat the solution until it gets to about 180°F. Use a candy thermometer to maintain the temperature of the solution between 180° to190°F. Do not boil the solution.

Once the solution gets to about 180°F, drop the degreased pad of steel wool into the parkerizing solution and allow it to begin dissolving. This primes the solution for your metal parts. Maintain the temperature of the solution at around 180-190°F.

Adding Your Metal Parts to the Parkerizing Solution
Once the steel wool is most of the way dissolved, add your steel parts. Maintain the temperature and allow your parts to begin the transformation. You should see bubbles where your parts are laying in the solution. The phosphoric acid will literally corrode your steel while mixing with the manganese dioxide to form a dark phosphate layer/coating over the steel. This is the parkerizing process. It is very similar to rusting but, if done correctly, will be beneficial to your metal.

You should check your steel parts every few minutes to see how far along it is in the parkerizing process. Eventually the parts should begin to bubble less as the parkerizing layer actually inhibits further corrosion from the acidic solution.

Parkerizing tray, solution and boiling water pot on stove.
Parkerizing tray, solution and boiling water pot on stove.
You may need to remove your parts to clean off the dark surface created by the process and then re-dip the parts in the parkerizing bath to continue the parkerizing process. The longer and more frequent you dip your parts, the darker and thicker the coating on them will become. However, it is important to understand that you are also stripping more metal off the surface of your parts.

Warning: Do not leave your steel parts in the parkerizing solution unattended for extended periods of time as the acid will literally eat away at them until your steel is destroyed. This is the part where you have to use some common sense. The longer the steel parts sit in the parkerizing solution, the more steel will be removed.

Remove, Clean and Hose Down Your Steel Parts With Oil!
Once you are content with the parkerizing layer formed on your steel parts, you will need to remove them from the parkerizing bath and neutralize the parkerizing solution. To do this, I simply washed my steel parts in a pot of boiling water for a minute or so. This should remove most of the phosphoric acid as well as keep the parts hot.

Remove your steel parts from the boiling water. They should air dry within seconds. Once dry, you will want to immediately submerge your parts in a quality water displacing oil. I highly recommend using a quality gun oil that has PTFE in it.

Let your parts soak in the oil for several days. You need to give your newly parkerized parts time to soak up the oil. Once the oil is absorbed into the newly porous surface of your steel parts, the parkerization process is complete! Be sure to regularly oil the steel parts you just parkerized and you should be able enjoy a long lasting, durable protective coating on your knife, gun or other steel parts.
Please share pictures of your parkerized goods in the comments section.

You may get several uses out of your parkerizing solution. When done dispose of leftover parkerizing solutions properly. Do not just dump it down the drain or toss it in the trash. You may neutralize your solution with baking soda but keep in mind your going to get a foaming reaction so doing it slowly in a large open bucket is probably best. 

1 comment :

  1. You should do a DIY on Reddit. Lots of people would appreciate this on there.


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