Blue liquid for rust prevention

[Suzuki4evr]

Hallo guys. What do you call the blue liquid I see on YouTube videos they use that makes metal turn black in color? They use it to prevent rust I think.

Michael

 

[benmychree]

If it is cold gun blue, it is nearly worthless for rust prevention; the one that I am familiar with uses a copper sulfate solution and another ingredient that turns the resulting copper color to black, on guns, it is used for touch up work, it is not durable.

 

[gwade]

The best I have found is oxpho-blue liquid from Brownells - https://www.brownells.com/gunsmith-...ld-bluing-chemicals/oxpho-blue--prod1072.aspx.

 

[Suzuki4evr]

Any other suggestions is very welcome.

 

[Martin W]

If you put your parts in Evaporust it will leave a black oxide finish.
Cheers
Martin

 

[pontiac428]

Zuki, it's usually phosphoric acid solution, with a bit of chromic acid in the mix to help the controlled oxidation reaction along. If you pre-heat the part (or solution) it will blacken almost instantly. It works well. I don't know if US brand names are of any help in SA, but the product itself is ubiquitous.

 

[GL]

Maybe I think I understand something I don't (could have read it on the Internet and everything's true there). My understanding is the actual surface treatment is not a good rust preventative, black oxide is only good for 10 hours of salt spray, but the porosity allows oil to soak in, which is the actual preventative. Does that follow with experience using cold blue products? It does look cool on shop made tools - but hey, that's also on the Internet.

 

[derf]

If you want something cheap and effective, try parkerizing.

 

[warrjon]

I heat the metal ( NOT to cheery red for hardening) and oil dip, this will turn the metal black and prevent it from rusting. I have done this with the feet I made for my granite surface plate and lathe so far no rust, and rust is a big problem here in winter.

 

[SamI]

Maybe I think I understand something I don't (could have read it on the Internet and everything's true there). My understanding is the actual surface treatment is not a good rust preventative, black oxide is only good for 10 hours of salt spray, but the porosity allows oil to soak in, which is the actual preventative. Does that follow with experience using cold blue products? It does look cool on shop made tools - but hey, that's also on the Internet.

I'd agree with that. I used Birchwood Perma Blue to blacken a lathe spider I made. I left it on the bench overnight and in the morning there was a little surface rust. Cleaned it up and gave it an oiling and 6 months later not a spot of rust. Any bare metal surfaces in my workshop need to be wiped down regularly and coated in oil to prevent rusting in winter. The cold blue solution takes the need for this regular cleaning away.