White rust is a naturally forming white deposit that develops on galvanized steel due to corrosion process.

Zinc products are susceptible if the surfaces become and stay wet while in a pack or bundle. Capillary action pulls water into the space between tubes where the absence of airflow contributes to the accelerated formation of naturally forming corrosion products.

White rust is most commonly encountered during transport and storage when material becomes wet and the trapped moisture between touching surfaces is unable to escape and is also referred to as ‘wet storage stain’.