White rust on galvanized coils costs the North American steel distribution industry an estimated $180 million per year in rejected material and rework. Most of that damage happens not at the mill, not in transit, but in your warehouse. Between the time a galvanized coil arrives and the time it ships to your customer, your handling practices determine whether it arrives pristine or covered in white oxide deposits that make it unsaleable.
Why Galvanized Is Different
The zinc coating on galvanized steel is softer than the base metal. It scratches easier, dents easier, and reacts with moisture in ways that bare carbon steel does not. When zinc gets wet and cannot dry quickly, zinc oxide and zinc hydroxide form on the surface. That is white rust. It is not just cosmetic. Heavy white rust compromises the corrosion protection that the coating was designed to provide.
Hot-dipped galvanized (HDG) is more forgiving than electrogalvanized (EG) because the coating is thicker, but both require careful handling. Galvanneal (GA), which has been heat-treated after coating, is the most sensitive to surface damage because the zinc-iron alloy coating is harder and more brittle.
Storage Rules That Prevent Claims
Store galvanized coils indoors. This sounds obvious, but we have walked into service centers where galvanized coils sit outside under a tarp. A tarp traps moisture. It is worse than no cover at all. If you absolutely must store outside temporarily, use open-sided shelters that allow air circulation.
Inside the warehouse, keep galvanized material away from concrete floors. Concrete wicks moisture. Use wooden dunnage, plastic blocks, or coil pads. Stack coils eye-to-sky when possible, with spacers between layers that allow airflow. Never stack galvanized coils directly on top of each other without separation.
Temperature swings cause condensation, which causes white rust. If your warehouse has no climate control, ventilation becomes critical. Industrial ceiling fans that keep air moving across the stored material reduce condensation significantly. A $3,000 fan installation can prevent $30,000 in white rust claims per year.
Handling Procedures That Matter
Forklift damage to galvanized coils is the second most common cause of customer rejections after white rust. The zinc coating shows every scratch, every fork mark, every ding. Train your forklift operators specifically on galvanized handling: use coil rams instead of forks when possible, pad any contact surfaces, and never drag a coil across the floor.
When slitting or cutting galvanized material, use tooling designed for coated products. Dull knives on a slitter will peel the zinc coating rather than cut cleanly through it, creating edge burr and coating delamination. Keep slitter knives sharp and properly spaced for the coating weight you are processing.
Inspection and Documentation
Inspect galvanized coils on receipt, not when they are about to ship. Document any coating defects, edge damage, or white rust with photos and note the coil ID, heat number, and location in the warehouse. If you find damage on receipt, file the claim with the mill or carrier immediately. Waiting two weeks to report damage that happened in transit makes the claim nearly impossible to win.
Your customers expect galvanized material to arrive with a clean, uniform coating. Meeting that expectation starts with how your team handles it every day. The training investment is small. The cost of getting it wrong is not.