recent posts



Preventing White Rust in Galvanized HVAC equipment

September 18, 2020

White rust is the enemy of cooling towers and other galvanized HVAC equipment.  Once white rust has formed, it can significantly reduce the life of a cooling tower if left untreated. 

White rust is a chalky substance that can form on the surface of some metals that include zinc when the zinc is exposed to hydrogen and oxygen. Newer galvanized steel products can react chemically to elements and water treatments to form the white rust.  This often happens to new evaporative units before they have a chance to undergo passivation, but it's best to prevent the formation of white rust before it ever starts.

Fortunately, Evapco offers factory pretreatment called Passiv-Assist® to assist with passivation to minimize the occurence of white rust.  Passivation helps equipment form a chemical film barrier against rust.  Benefits of Passiv-Assist include:

    • Enhanced speed and effectiveness of properly executed field passivation, including replacement units requiring immediate heat load
    • Field passivation tailored for each location and the site-specific makeup water quality
    • A network of Factory Authorized Water Treatment Partners trained to assist in field passivation
    • Facotry mounted Pulse-Pure® and Smart Shield® systems are designed with ports to aid in passivation field panel install
    • Passivation plan promotes the formation of a passive oxide layer, eliminating the need to feed white rust inhibitors for the life of the unit

Evapco offers a two-step process for their galvanized steel cooling towers.  The first step is the Passiv-Assist factory applied pretreatment.  After a new coil is hot-dipped galvanized, EVAPCO applies a proprietary chemical pretreatment.  Coils that receive this pretreatment consistently develop less white rust than untreated coils across a wide range of makeup water qualities and water treatment programs.  While the pretreatment does not provide a completely passivated coil, it does make field passivation faster.

The second step is field passivation, using Factory Authorized Water Treatment Partners with the installing contractors.  The field passivation includes EVAPCO inhibitor chemistry, feed and control equipment and routine service visits by a local Water Treatment Partners.  This process takes 4 to 8 weeks, taking less time than other field passivations taking up to 12 weeks or which require a white rust inhibitor to be fed throughout the life of the evaporative cooling equipment.

The results?  See for yourself!


Evapco Passiv Assist

No matter the application, the EVAPCO passivation solution works across a wide range of makeup water qualities and offers great results!

Click to learn more about  Passivation and White Rust


// about the author
Kelly Patterson

Kelly Patterson

Kelly Patterson is a lifelong learner and the marketing director at the Hoffman family of companies. There is nothing she likes more than talking about commercial HVAC systems and extraordinary customer service.

// share this post