Efflorescence is best described as which of the following?

• A. A rust inhibitor applied to metal surfaces.
• B. A decorative effect produced by salt crystals.
• C. Atmospheric salt residues, which is a surface contaminant that reduces adhesion and causes blistering, peeling, flaking and under film rusting.
• D. A solvent-based coating additive that improves adhesion.

Answer: (C)

Efflorescence is atmospheric salt residues that form on a surface when moisture moves soluble salts to the surface and they crystallize as the water evaporates. On painted or coated metal surfaces in marine environments, these salts become a surface contaminant that interferes with the bond between coating and substrate. That interference weakens adhesion and can cause blistering, peeling, and flaking of the coating, and it can promote under‑film rusting because the salts provide an electrolyte path for corrosion.

To handle it, remove the salt deposits by mechanical cleaning or washing, rinse thoroughly, and allow the surface to dry completely before repainting with a compatible primer and topcoat. Address the moisture source to prevent recurrence. This description fits efflorescence, whereas rust inhibitors, purely decorative salt effects, or solvent additives do not describe this phenomenon.