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Ted Mooney, P.E. RET
The authoritative public forum
for Metal Finishing 1989-2025
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Ospho prep left tacky film
Q. I've applied Ospho to a painted van floor that had rust bleeding through as well as bare metal in spots. Prior, I sanded the entire surface with 100 and 240 grit paper. After the Ospho, I washed with mineral spirits. But the floor is tacky and I'm afraid to prime and paint. What should I do? Do I wait longer for Ospho to dry? Have already waited 36 hrs. Do I wash with soap and water, and will washing get tackiness off? Or do I prime and paint, and will paint seal tackiness or will it just make more of a mess? Thanks for your suggestions.
Anne snyder- Mount Horeb, Wisconsin
September 8, 2024
A. Hi Anne
Ospho is intended to react with bare metal. Apparently when applied to a painted or lacquered surface the acid in it can react with certain paints and produce this gummy effect.
If Skyco has no advice for you I would suggest washing/scrubbing it off with a scrub brush
⇦ this on
eBay or
Amazon [affil links] and a strong detergent like Spic and Span
⇦ this on
eBay or
Amazon [affil links]
, and then painting. The detergent won't hurt the rusted and bare steel surfaces which received the Ospho conversion coating. It should all come out fine.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
⇩ Related postings, oldest first ⇩
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 [adv: Ospho on eBay or Amazon [affil links] , 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 ⇦ this on eBay or Amazon [affil links] ?
Larry Asche- Gladstone, Oregon
A. Hi, Jay. Everything is a compromise, and I think Ospho "works" on galvanized steel but its 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 but reacted with the lacquer?
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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
- Dallas, Texas
September 20, 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 is painted or has a clear coat on it such that the Ospho didn't reach metal but is just reacting with the clearcoat and turning it gummy?
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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