Rust Off®

What is Rust Off?

Rust Off rust and oxide film remover restores metal to a ready-to-coat surface. This convenient gel formula (easily mixed with water) makes quick work of removing rust and film. Rust Off should be diluted at a rate of 1 quart per 5-gallon bucket with water and applied at a rate of 400-500 square feet per gallon.

If it is gelled in the container, Rust Off can most likely still be used. Try mixing in warm water to aid in returning Rust Off to solution form.

How long should I leave Rust Off on metal surfaces before removing?

Rust Off is a concentrate. First mix one part Rust Off with 20 parts water (1 quart of Rust Off per 5-gallon bucket of water). Rust Off contains acid, so please ensure that the proper personal protective equipment (PPE) is being worn. Apply liberally with a brush or a rag.  

Rust Off takes about 10 minutes to work, and all scrubbing and power rinsing of the substrate should occur before the material has dried.   

Make sure to check all codes and disposal requirements in your area with regard to capturing the mixture that is being rinsed off the roof. 

What will happen if I don't use Rust Off?

Encase Metal Primer is a rust-inhibiting coating. This product helps prevent the formation of rust on properly prepared surfaces. It doesn’t convert or remove existing rust. There may be premature failure of the coating if applied over existing rust.

Benchmark®, Rapid Roof III®, Rapid Roof® HV, Puma®, Equinox®, Puma® XL and Prime Time® are not designed to inhibit rust. Any existing rust will go through these coating systems.

If a metal surface has been sandblasted, the newly exposed iron surface is extremely susceptible to rusting. Rinsing with tap water or applying a latex coating can lead to "flash rusting," which is rust from iron bleeding through the coating. This bleed-through causes a stain, which can range in appearance from a light yellow discoloration to heavy orange or red spotting and staining. Flash rusting occurs when a thin film of water, either pure or in a water-based coating, stays on the steel surface for a short period of time. Flash rusting is apparent within hours, unlike long-term corrosion, which takes days or years to appear.

The sandblasted surface should be cleaned with Rust Off to prevent flash-rusting. Encase Metal Primer is resistant to flash rusting, but may not have enough protection if applied to sandblasted steel that has not been treated with Rust Off.

I'm preparing a metal roof for a coating application. When is it necessary to use Rust Off?

Rust Off has a number of important benefits when used to prepare a metal surface. Rust Off dissolves loose rust, helping to prepare a good surface for coating. The phosphoric acid in Rust Off bonds with the metal surface, passivating or chemically tying up rust and making the surface more resistant to later rust. This is very critical in areas that have been wire brushed or sand-blasted to bare metal.  Basecoats and primers have better adhesion to the Rust Off treated surface.

Steel or Iron (Fe) + Oxygen (O) ---> Iron (2) Oxide (FeO) (red and water soluble) 
Iron Oxide (FeO) + Phosphoric Acid (H(3)PO4) ---> Iron (3) Phosphate (FePO4) (black and insoluble)

Heavy rust must be removed by wire brushing, scraping, or sandblasting. All cleaned areas and lightly rusted areas must be treated with Rust Off to remove any remaining rust. Remember that there is always light rust on weathered iron and steel surfaces, even if it isn't visible. This light rust, if not treated properly, will cause early coating failure. Failures can include red rust bleeding and adhesion failure.  Additionally, all new galvanized surfaces must be treated with Rust Off.

What prep work is needed before recoating when there is rust coming through the previous coating?

All of the rust, and any coating over the rust, needs to be removed. Coated metal cannot be treated with Rust Off to remove rust underneath.  

The roof must be sandblasted or wire brushed all the way to clean bare metal. The exposed metal should be cleaned with Rust Off, rinsed with clean water, and coated with Encase Metal Primer.

Will Rust Off or Multi-Surface Cleaning Gel™ harm grass or plant life?

Yes, Rust Off/Multi-Surface Cleaning Gel may harm or kill grass and plants. We recommend using caution when cleaning outdoors. Avoid grass and plants when possible. Cover plants with clear plastic and water thoroughly immediately after removing plastic.

All materials that come off of the roof or the walls should be disposed of in accordance with the local county, state, or federal regulations that govern this application.