[Breaking Taps] has a look at “parkerization” — a process to coat steel to prevent rust. While you commonly see this finish in firearms, it is usable anywhere you need some protection for steel parts. The process is relatively easy. It does require heat and a special manganese solution made for the purpose. You scuff up the surface of the steel and degrease and wash it.
Once the part is ready, you insert the part in hot solution which is manganese and phosphoric acid. Rinse and displace the water and you are ready to oil the part.
But what we really liked was the electron micrographs of the steel before and after the process. The phosphates formed in the solution cover the iron and hold oil to prevent oxidization. However, the first attempt wasn’t uniform so it wouldn’t work as well. [Breaking Taps] thinks it was a failure to rough up the piece sufficiently before starting. He also raised the temperature of the bath and got a better, but not perfect, result.
We miss having an electron microscope at work and we really want one at home! The last fun coating project we remember used copper in a strange and wonderful way.
I am not saying this is exact same process as blueing. But seems quite similar (maybe except for the fact blueing uses iron oxide crystals instead of phosphate crystals). Are there any practical differences in quality of resulting finish?
Also it would be cool to see microscopy of surface wetted with oil.
Nice to see those surface structure photographs. According to Wikipedia, they use a 95 °c temperature, Which is basically as hot as you can get without boiling.
https://en.wikipedia.org/wiki/Manganese(II)_phosphate
For the pickling process. Probably good to add that too. I once was curious and put a piece of cold rolled steel into a jar of vinegar, then forgot it for about a week, All the millscale had disolved, and it etched the steel deep enough to expose cristal structure and there were even some quite deep etched grooves in the length direction. Vingear works, but a week is too long for de rusting / cleaning mild steel.
I once left a rusty old tool in phosphoric acid de-rust solution for about a week, it dissolved the rust and then some of the tool, weakening it.
B^(
What about Cerakote?
I drop the parts off one day, then the next day (plus a little bit of money) I get the Cerakoted parts back. Here’s how it works:
What Is Cerakote & How Is It Applied?
https://www.youtube.com/watch?v=FiW_SUi9-8E
Cold blueing works pretty well too, and it is a lot less work. Wipe on the solution, wash off and coat with oil.
I have done a few (hobby level use) parts this way and no rust after a year or so. And I don’t have any EM micrographs :(
Geoffrey Croker has one of the best most straightforward videos on DIY electroplating out there, as simple as you can get and works well:
https://www.youtube.com/watch?v=G-PtnwtOR24
Nickel, Copper, Zinc in this video. Also of interest is the same process to remove rust by electrolysis, again super simple but very effective.