Wet Storage Stain vs. White Rust
Many people perceive wet storage stain to be the same as white rust and use the two terms interchangeably, but they do have distinct differences.
Wet storage stain is the commonly known problem of white surface oxide formed on newly galvanized steel due to packing the items too tightly and/or storing in a humid environment. If moisture can bridge the gap between galvanized pieces, the local shortage of oxygen created by this moisture can set up a galvanic cell that will give rise to rapid attack at those places where oxygen is deficient.
White rust, on the other hand, is associated with cooling towers. Cooling towers were first galvanized in 1965, but the white rust problem was not noticed until 1986. The older towers and unaffected towers all received a chromate treatment after galvanizing. In the mid 1980s more stringent environmental restrictions prevented the use of chromate treatments and white rust developed on the cooling towers. White rust has been identified as basic zinc carbonate.
Wet Storage Stain Publication
© 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.