making parkerizing solution

[Teus]

Hi all,
I'm trying to parkerize knives. I'm from Europe and parkerizing fluids aren't available here, and you can't simply ship or transport them from the USA since it's a hazardeous material.
I went to buy 1L of 75% phosphoric acid. To make 500ml of solution, I mixed 10ml of phosphoric acid with 20-30ml of distilled water and added 3gr of manganese from alkaline batteries and 5grams of steel wool that was cleaned with acetone. It started producing gas and smelling awful. Once the reaction ended I added more distilled water, heated to 80C, added the knife. I did a lazy job at sanding the knife, but the knife was cleaned with isopropyl alcohol and washed in distilled water. The solution was kept at 80-85 celsius for 30 minutes. Knife was removed from the fluid, washed in distilled water, blown dry with canned air and coated in WD40.
I got to this point after research and some experimenting. The process seems to have worked, the coating seems hard enough. Sanding the coating away is hard, and with another knife I can only make tiny markings. Photos below

Some questions:
a) why do a lot of guides say to add iron to the solution, if I just want manganese parkerizing?
b) why does the phosphoric acid react violently with steel wool, but seemingly does nothing when I add manganese recovered from scrap batteries? should I order manganese dioxide powder online to see what difference it makes?

 

[eKretz]

The "homebrew" Parkerizing solutions I've tried used a lot more acid, MnO2 and steel wool than you did (for a gallon of solution the recipe I like uses 2oz. of acid and about the same volume of MnO2. Then once everything is up to temp, add a degreased steel wool pad and let it cook for 10 minutes then remove it and start phosphating - I'm not sure why some of the homebrew solutions call for iron filings - it's my understanding that when using a manganese solution you want to avoid any iron phosphate forming. Your temp is also lower than what I've used as well - I try to hover around 200ish°F or 93°C. Best results are supposed to be just below boiling.

 

[Teus]

okay, thanks.
I just reviewed everything again, and apparently I was recovering the zinc anode from the battery (gray goo) instead of the manganese dioxide cathode (black hard crumbling stuff).
I also found out you can use nitrate acid to speed up the process. the site agrees with the "below boiling point" temperature, while a lot of other sources list 70-80 celsius
http://www.phosphating.net/manganese-phosphating.html

 

[eKretz]

Yup, you want the black cylinder that's formed against the outer part of the battery and break it up as fine as possible. The higher the temperature you can reach without boiling the faster your parts will get done. I'm not sure if the temperature actually makes any difference to coloration or anything else. I once read a patent filing for a method of Parkerizing that was supposed to be twice as fast as the normal method - the Park solution was maintained at over 500°F IIRC! I don't recall what they mixed into the solution to keep it from boiling at that temp - or perhaps they just used the vapor.

 

[Teus]

oh, maybe they use pressured vessels to do the job. KFC uses pressurised deep fryers so they can fry at a higher temperature.
my new attempt went very well, I call it a success. I didn't use steel wool at all, but the battery crumbs do contain things like a bit of iron. now I can order pure manganese instead of doing it the ghetto way. should I get manganese dioxide or manganese sulfate?
I read the following: the longer you parkerize the metal, the more metal you're eating away and converting. since the phosphate coating is porous, I assume the acid eats it's way into the knife through the coating?

here's a photo

 

[eKretz]

Ah yes, that could well be - pressure vessels would probably work great. That attempt looks much better. Now you need to oil it and it should blacken nicely. When I have used this method I always use manganese dioxide, and I will periodically lift out and replace the parts while hanging from a wire, this helps keep the smut off. I keep mine in the bath about half an hour. The shorter it's in the bath the lighter the color will be; the longer, the darker. At high temps 40% or stronger solutions of phosphoric acid will really chow down on steel, that's why it's important to not use too high of a concentration. At the reduced strength used for our purposes though (2 oz. per gallon in mine) you'd have to leave your parts in for quite a while to worry about much dimensional change.