Evapco Has Spent 50 Years Perfecting Passivation and How to Avoid White Rust

Evapco has over 50 years of experience in the evaporative cooling industry utilizing galvanized steel. Galvanized steel has been the material of choice since the 1970’s to prolong the life of evaporative cooling equipment. Passivation extends the integrity of the steel and staves off white rust.

Galvanization layersThe Galvanization Process

The galvanization process occurs when the metal (in this case, steel)is dipped into molten zinc. The steel and zinc then form a metallurgical bond. This type of bond creates layers of alloys with varying compositions. The galvanization process of melting metals together to create layers offers unmatched adherence and ductility.

Rust is The Enemy

Rust is the result when oxygen and moisture meet iron. Imperfections in the metal are susceptible to rust because metal has small anodes surrounded by large cathodes. Moisture collects at the cathodes, and the large surface area breaks down the material faster. Galvanization was created to solve accelerated breakdown.

White Rust


The result of galvanized steel, oxygen, and moisture is white rust. The size of the cathodes is significantly reduced in galvanized steel. Zinc covers the anodes. The cathode exposes a lower layer of an alloy and occupies less space than on ungalvanized material.

How Can White Rust Be Slowed?

Evapco started extensive research in the 1970s into how to prolong the life of galvanized steel. They developed specialized equipment to test white rust formation on galvanized steel and treated it in a number of ways. Evapco was able to identify how the passivation process benefits and prolongs material life.

The passivation process naturally develops a protective layer on galvanized steel. This layer is an oxidated zinc that extends the service life of the material to 30+ years. When sufficient contact time with the atmosphere maintained through ongoing water treatment causes natural passivation. Additionally, to ensure the material’s longevity, it is vital to work in commissioning time for natural passivation.

Watch Evapco’s educational video below for more extensive information on how passivation works.

For more information on Evapco’s evaporative cooling equipment or other products, please contact your SVL Sales Representative or click here.