bear with me as I'm just a hobbyist- If i have any serious flaws with what I'm doing let me know
I have some small (OD 1.5" ID varying .5" or a bored cone) steel parts I want to coat without paint, (cheaply and relatively safely)- I read many archived threads about blackening steel and found many alleged possible methods. I decided to try the following: heat with a propane torch until a dull red, then submerge into corn oil and wait for bubbling and smoke to stop. Then heat to red and submerge again. Then take out and burn off oil and allow to cool slowly.
The first time I did it I misread the post and after the second submerging i took it out, wiped off the oil, and cooled it in water (I was impatient) It left a matte dark gray finish with a blue tinge in the light that I was rather satisfied with (although I'd prefer really dark black) That was a couple weeks ago- I noticed some spots already starting to oxidize (rusty colored- not black) today so I went back to the archives and realized what I did wrong. I again heated until dull red and submerged twice then tried to burn off the extra oil. This time some of the surface had a similar nice finish as before although darker and more even- however some of it had a jet black shiny covering that I really liked. I suspect that the shiny black was carbon residue left from burning the oil but I'm not sure.
Most importantly I want an even finish that will be rust resistant. What can I do differently to get that surface?
Part of my problem may be I sometimes work at night, sometimes during the day. The propane torch is not hot enough to make the steel visibly red during the day so I guesstimate when to dunk in oil, however at night I can see it glowing. Should it be glowing red even in broad sunlight?
Any suggestions with this method?
One last related question. Using the propane torch with something like that, what surface would you recommend working on? Slate chips and sends sharp shards when too hot, should I be on stone? Thick metal? What about a slab of concrete (making sure to minimize air pockets)?
Thanks for any help, I need it Jonathan Battat