Wet Storage Damage

Close stacked sheets may deteriorate quickly if water enters the pack. This happens because the metal exposed to moisture without air forms bulky, unstable, and loosely adherent, hygroscopic compounds. See Crevice Corrosion/Wet Storage Stain.

Water can infiltrate deeply into a bundle of close-stacked sheets. The extent and severity of wet storage stain is usually proportional to the time the sheeting has been wet, however, the time to onset can be very variable, and occur more rapidly in warm conditions. 

Sheets can be dried by filleting sheets or cross-stacking them on a slope to allow water to drain and air to circulate between them. Only use a dry, well-ventilated environment for long-term storage.

A patchy visual appearance of the paint can also result from wet stack storage of pre-painted steel products. This is known as blooming.

Blooming results from water swelling the paint and flattening or suppressing gloss components. The gloss distortion is typically temporary and will dissipate with time, and exposure to heat/sunlight. This can be demonstrated by the application of boiling water to an affected surface bringing the appearance back to normal