View Full Version : Passivating rust

Ian B
04-14-2006, 11:10 AM
I've used the phosphoric acid passivating gels on various bits of rusty iron & steel with good results. Is there any reason why it shouldn't be used on items that get hot? I'm thinking about doing the hot side of the turbocharger & exhaust manifold (or headers for those on the other side of the pond) of my excavator & tractor.



04-14-2006, 01:21 PM
If you use the thin liquid product, like OsPho, and paint it on the header it should react with the rusty material and form a glasslike coating. I think all of the reactive agents are used up at this point. You would be better off to get a pint of POR-15 Black Velvet, however. I used this stuff on the manifold of my old army truck and it totally stopped the rust. It is a ceramic based coating and does a great job.

Jim (KB4IVH)

04-18-2006, 02:16 AM
Hi, I'm restoring a '56 GMC 3/4 ton pickup, and running an '85 1 ton crewcab, and have many occaisions to deal with rust. I was talking to a mechanical engineer friend who is in manufacturing, and he said the phosphoric acid rust neutralizers could make the steel brittle-which made me more cautious about acid treatments. I've heard great things about POR-15, have to try it one of these days. I wonder if anyone else has heard of this embrittlement process?

04-18-2006, 12:26 PM
Do yourself a favor and get a gallon of Evaporust. No acids, gets the rust off without hurting anything.

Ian B
04-19-2006, 01:07 PM
Thanks Rex - it looks like good stuff. I live in the Netherlands - I'll try to find a dealer here.