Wash the Blush Before You Sand It

The Wet Edge, No. 005. Short field notes for coating crews.

You come back in the morning and the epoxy has a greasy film, a white haze, or a waxy feel. That's amine blush, and it's one of the few coating problems that washes off.

Blush forms when the curing agent reacts with moisture and carbon dioxide at the surface before the film cures. Cold, damp nights set it up. So do direct-fired propane or kerosene heaters in a closed space, since they put out both. Some products blush more than others, and you can't always see it.

Why it matters: topcoat over blush and you're asking for an intercoat adhesion failure. The next coat looks fine, then lets go between coats.

Here's the catch. Blush is water-soluble, so a solvent wipe doesn't do much, and sanding first just grinds it in. Scrub it with warm water and a detergent, rinse well and let it dry. Then abrade if the recoat window has closed. Field test kits exist if you're not sure it's there, and the manufacturer's cleanup procedure comes first.

Better yet, keep the steel above the dew point through the cure, and keep direct-fired heat away from fresh epoxy.

Bottom line

Blush is water-soluble. Wash it with warm water and detergent before you sand or recoat, and keep direct-fired heaters and cold, wet nights away from fresh epoxy.

Further reading: Causes, Detection, and Removal of Amine Blush (KTA-Tator).

Talk to a consultant. Questions on a job? Atlantic Coating Consultants supports contractors in PA, NJ, DE, MD, DC, WV and OH with product recommendations, field support and crew training. Call 484-644-5303 or email atlantic@tnemec.com.