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topic 22903

Ospho prep left tacky film


A discussion started in 2003 and continuing through 2020 so far.
Adding your Q. / A. or Comment will restore it to our busy Current Topics page

2003

Q. I wire brushed, scraped, and cleaned some wheels off a 1980 Renault LeCar, which I think are galvanized steel, or at least zinc plated. I then sprayed on Ospho [affil. link to product info on Amazon], which is a phosphoric acid solution, and waited overnight as per the directions. The rusted areas did turn blackish and seem to be ready for paint, but the clean, unrusted surfaces seem unaffected and have an uneven, blotchy, clear gloss film which is a bit tacky in spots. The directions say it will etch the metal, and leave a dry powder, but I see no powder at all. How can I tell if the metal has been etched? Has anyone else used Ospho on clean metal and what was the result? If I paint over the tacky film and the paint also stays tacky, I'll have a real mess.

Jay Proctor
- Lehigh Acres, Florida


2003

A. Aren't you supposed to rinse before painting? or use a Self-Etching Primer [affil. link to product info on Amazon]?

Larry Asche
- Gladstone, Oregon


A. Hi, Jay. Everything is a compromise, and I think Ospho "works" on galvanized steel but it's real strength is on rusted steel. Ospho suggests washing or wiping off the material after half an hour for nicest results on galvanized. In any case, I would now wait until it thoroughly dries, even if that is several days. Good luck.

Is there any chance that your "clean unrusted surfaces" actually have some sort of clear coat on them so the Ospho didn't even reach metal?

Regards,

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha



September 20, 2020

Q. I have painted Ospho on my aluminum garage door. However, after 24 hours it is still tacky. Am I supposed to paint the base coat when it is tacky or wait longer? Do I need to clean the door with mineral spirits?

This is my first project using this product.

Thank you,
Maria

Maria Clayton
- Dallas, Texas


September 2020

A. Hi Maria. Ospho is supposed to be usable on aluminum, so I'm not sure what went wrong. Is it possible that the aluminum has a clear coat on it such that the Ospho didn't reach metal but is just turning that clearcoat to gum?

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading

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