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Prevent White Rust ON Cooling Towers

June 19, 2020

Galvanized steel has been the preferred material of construction for evaporative cooling equipment for over 50 years. However a form of premature zinc corrosion, known as white rust, can occur on new galvanized surfaces. White rust can significantly damage the galvanized coating and mar the appearance of the surface. 

Galvanized surfaces need to develop a protective oxide layer through the process called passivation, to help minimize white rust. Unfortunately, equipment operators do not have time to passivate before operating their equipment, as the process can take anywhere from two months to two years. After six years of research, Evapco has designed a 2-step process that reduces the potential for white rust formation. Evapco has introduced Pass-Protect passivation solution featuring Passiv-Assit for galvanized coils.

Here is the two stop process outlined by Evapco:

Step 1: Passiv-Assist Factory Applied Pretreatment

After a new coil is hot-dipped galvanized, EVAPCO applies a proprietary chemical pre-treatment which substantially reduces the potential for subsequent white rust formation. Coils that receive the factory pre-treatment consistently develop less white rust than untreated galvanized coils across a broad range of makeup water qualities and ongoing water treatment programs. The factory pre-treatment does not provide a completely passivated coil. It does, however, make field passivation faster and yield better results. The coils are then assembled into the custom condenser or fluid cooler and shipped to the customer.

Step 2: Field Passivation

EVAPCO coordinates the field passivation service through their network of Factory Authorized Water Treatment Partners and the installing contractor. The site-specific field passivation service includes EVAPCO inhibitor chemistry, feed and control equipment and routine service visits by a local Water Treatment Partner. This usually lasts between 4-8 weeks whereas other properly executed field passivations can take up to 8-12 weeks or require white rust inhibitor to be fed throughout the life of the evaporative cooling equipment.

For additional information and knowledge on passivation and white rust, watch the video below!

content and video from Evapco

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Marketing Department

Marketing Department

The Hoffman & Hoffman marketing team is always looking for ways to educate our customers on HVAC use & efficiency.

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