Oxpho Blue is it just phosphoric acid?

[bluebayou]

If I darken a damaged barrel with phosphoric acid will it be as effective as a cold blue product like Oxpho Blue or Perma Blue?

[John Traveler]

Applying phosphoric acid to a raw steel surface will normally produce a dark gray phosphate finish covered with grainy black oxide particles.  The black oxide will quickly rub off with a little rubbing.  The various cold blues will give a more durable darker finish, although not as durable as a hot blue or rust blued finish.

[bluebayou]

My uncle was using some kind of phosphoric acid based  compound on a car body.  I was thinking, hmmmmmm.

What you describe doesn't sound very durable.  He was just doing it before priming...thanks anyway.

[Keith L]

I don't know about car painting or use with guns, but I do know we had a phosphate bath in the power washer we used to prepare steel parts for paint in several factories where I worked.  It was used for a bonding agent prior to prime and paint operations.

[bluebayou]

I wonder if that would help adhesion with Duracoat or Brownells type finishes?

I used white vinegar as etching solution on an aluminum boat that I was spray can painting, and it seem to help.  Was a lot cheaper than using self-etching primer thats for sure.