OSPHO is easily effective for exterior and interior work alike. OSPHO safely dissolves bleeding rust from many painted surfaces. For best results, use OSPHO at temperatures no lower than 36°. Excess dew and humidity may prolong drying time, cause a reoccurrence of the drying process resulting in a powdery buildup.

What does OSPHO do to rust?

RUSTED METAL OSPHO is a rust inhibiting coating-NOT A PAINT. Merely remove loose paint and rust scale, dirt, oil, grease, and other accumulation with a wire brush or pressure washer and let dry- apply a thin coat of OSPHO as it comes pre-diluted in the container. Let dry for a minimum of 24 hours, then apply paint.

Can you paint directly over OSPHO?

Before applying, use a wire brush or wire wheel to remove loose paint, rust scales, dirt, oil, and anything else accumulated on the surface. After doing this, apply a coat of Ospho and let it dry (overnight). Once the surface is dry, you can paint over it.

Do you have to rinse off OSPHO?

When the intention is to leave ospho on the panel for protection, it still has to be wiped off with a dry rag, leaving only a thin film. This would be in the case of protecting the bare metal during the body working process, and when ready for paint then it should be rewet with a scotch pad and rinsed off completely.

Why does Ospho turn white?

A. Hi Jim. says “A dry, powdery, grayish-white surface usually develops; this is normal – brush off any loose powder before paint application.” I don’t think sanding is necessary but brushing with a wet scrub brush is probably a good idea.

Does Ospho expire?

Re: OSPHO Shelf Life

It says Ospho is stable when stored. It is a form of phosphoric acid, so the MSDS claim is likely valid, provided the container is still intact.

How long does it take Ospho to dry?

12 hrs or overnight usually does it. It turns light gray then go over it with a fine scotchbrite pad, blow it off and prime & paint.