Ospho Metal Treatment is a rust converter that contains phosphoric acid
Ospho Ospho Metal Treatment
  • Ospho Metal Treatment is a rust converter that contains phosphoric acid

Ospho Metal Treatment

Ospho resists and retards rust while providing a sound base for paint. Recommended for use under oil base paint or primer. One gallon of Ospho covers 600 sq. feet. It dries overnight, makes a lasting bond between rusted metal and paint. (Note: Ospho is not actually a paint.) Contains phosphoric acid.
$15.97 / qt
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Tech Spec Product Info User Generated Content

Rusted Metals:
It's important to note that Ospho is a rust inhibitor coating and not paint. 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.

How does it work?

Ospho transforms rust to iron phosphate, an inert substance. You will know its doing its job when the metal turns black. This means the chemical change has occurred. Very heavy rust can require two coats. Sometimes, a dry, grayish white powdery film develops. Simply brush off before painting.

Bare or New Metal:
Make sure new metal is clean and free of oils or grease before applying Ospho. After drying overnight, the surface is ready for paint.

Galvanized Metal
Treat galvanized metals differently, depending on how important appearance is. If appearance is important, apply a singe coat of Ospho and let stand for 30 minutes or until metal is etched. Flush with water or wipe to a smooth finish. Once dry, the surface is ready for paint.

If appearance doesn't matter, disregard the above. Simply apply a single coat, let dry overnight, brush off powdery residue, and paint.

Painting Over Ospho

Painting treated surfaces tends to yield more durable finishes, as moisture and oxygen are effectively sealed away from the metal. Unlike thick paints, Ospho is as thin as water, going on easily and providing much more coverage (about 600 sq ft per gallon).

This metal treatment works best with oil based paints and primers. Be sure to test before using with epoxy or latex paints. Suitable for use indoors or out.

Additional Instructions, Recommendations & Tips:
For best results, do not apply Ospho below 36 degrees F. Also, excessive moisture or humidity may cause longer drying times and increase powdery residue buildup.

BRAND: Ospho
Type: Rust Converter
4.9 33

Ospho Metal Treatment Fantastic stuff


Pasture fence for horses, 7 acres. Easy to apply. I haven't found anything that is not so great about this product.


Linden, CA


Outstanding product for rust control


I've been using this chemical since about 1987. I haven't found anything that comes close to matching it's performance for what it is intended. It was recommended to me by a friend that restored old cars. I needed it to control rust on the underside of a motorhome. Since then, I use it when ever I'm repairing any metal prior to finishing.

86-year-old Chief General Flunky

West Virginia


Great product


I have been using Ospho since 1979, while in the Coast Guard. If you have use scaly rust, brush or scrape it away. Then simply apply. Best used in direct sunlight or under an infra-red lamp. The deeper the rust, the darker the finished area. No primer needed for painting. The iron phosphate result is over 90% as strong as the original metal.


San Fransico Bay, California


Engine Room Touch Up


We live in South Texas and the Humidity is always high. It is a constant battle against rust on our engine and brackets in the engine room. We have white painted Detroit engines so the rust that forms shows up very quick. We have been using this product for years. Wether you are doing a complete paint job or just doing some light touch ups. This product stops rust in its tracks. It is excellent in preperation. It can be a little messy if your not careful. Since it has the consistancy of water, if you apply on a verticle surface it may run off. I try to get the rust off with a wire brush and light sanding. Then apply the product with a foam brush. Then allow it to work. It's that simple. I usualy give it a day, then light sand if needed and wipe clean with a rag. Then apply paint. You will notice the rust turns from a rusty red to a darker charcol or black. It is an awesome product. I would recomend to all. A little of this goes alog way.


Rockport Tx


tried the rest this is the best


I am a serious metal detectorist and coin hunter and for years I have been searching for the perfect cleaner for old coins that I have dug -up . after being in the ground for sometime most coins except gold get a black tarnish on them which is near to impossible to clean off . I have tried everything suggested by other detectorists and to my amazement I discovered Ospho rust converter , after soaking the coin in Ospho for only 10 mins and a vigorous scrub with a toothbrush the coin is as clean as it was new athough not as shiney , putting the coin back into circulation . badly damaged or pitted coins are beyond salvaging no matter what you do

Pirate Treasure



Best metal prep I have found.


I have been using Ospho for years and I have not found a better rust killer, paint primer yet.


Baton Rouge, LA


Ospho rust killer


I use this product for a rust killer in old cars that I restore.


Coin, Ia.


I'll be placing another order soon.


I restore old automobiles and this product is excellent for rust removal and metal prep.


San Jose, Ca


The best cleaner for steel and teak


I used Ospho for over 22 years of maintaining cruising sailboats in the British Virgin Islands. Absolutely the best for maintaining the engine and all steel parts, including those which stained or rusted under load. While cleaning the support frame for teak swim platform I found it cleaned the teak platform better than anything else.


Gilford NH


Ospho saved my old galvanized gutters


I am currently preparing the battery area of my sports car's engine compartment with Ospho. It is great and solves many elaborate issues that come from sanding and killing semi-invasive rust caused by battery acid. Also, about 10 years ago, I used Ospho to etch the inside of my 45 year old galvanized gutters. They had small holes in them and were very rusted. I used Ospho to kill the rust after using a wire brush, and then lined the gutters with plastic-based roof sealant and plastic mesh strips. Saved me close to $1000 for new guter sat the time and it lasted for years.

Phil the fix it guy

Atlanta, GA


Ospho Metal Treatment



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