How to Clean Wet Storage Stain
Treatment of wet storage stain begins with drying the galvanized surface. As long as water remains on the zinc surface, and airflow is limited, the corrosion mechanism responsible for wet storage stain will continue, and can damage the zinc coating and underlying steel.
After the galvanized surfaces are dried, the treatment processes differ depending on the severity of the wet storage stain. Wet storage ranges in severity from light to medium to heavy. After drying, light wet storage stain can be left to weather as long as it will have adequate airflow. The wet storage stain will convert to a zinc patina as it reacts with carbon dioxide in the air. If the airflow will be restricted, or the surface is likely to have more standing water on it, then the wet storage stain must be removed by brushing it off with a stiff-bristled nylon brush.
Medium and heavy wet storage stain must be removed in order for the galvanized coating to form the zinc patina, otherwise the service life of the zinc coating and underlying steel can be affected. After removing the wet storage stain by brushing with a stiff-bristled nylon brush, and an appropriate cleaning solution, it is best to measure the zinc coating thickness to ensure an adequate zinc coating remains on the base steel. When medium or heavy wet storage stain becomes black, a significant amount of the zinc coating has been consumed and the steel must be stripped and regalvanized to meet ASTM specifications.
© 2019 American Galvanizers Association. The material provided herein has been developed to provide accurate and authoritative information about after-fabrication hot-dip galvanized steel. This material provides general information only and is not intended as a substitute for competent professional examination and verification as to suitability and applicability. The information provided herein is not intended as a representation or warranty on the part of the AGA. Anyone making use of this information assumes all liability arising from such use.