Coating defect

Dry spray

A rough, sandy, matt surface. The droplets dried before they reached the surface and did not flow together.

Dry spray: the surface as you see it, and a schematic cross-section.

Causes

Gun too far from the surface, or wind and high air temperature.
Very hot steel: the solvent flashes off before the film flows.
A thinner that evaporates too fast.

Prevention

Keep the gun distance and use the thinner for the conditions.
Respect the maximum surface temperature. Work in cooler hours or shade the steel.

How it is assessed

Visual and by touch. The film is porous, so a coat applied over it may fail. Check the DFT: the porous layer can give a reading that looks right while the film protects poorly.

Telling it apart

Overspray: Overspray is dry spray that landed outside the area being sprayed, on nearby steel.
Orange peel: Orange peel is a smooth, joined film with dimples. Dry spray feels like sandpaper.

Repair

Abrade or sand off the loose, rough layer before the next coat. The specification and the coating manufacturer have the final word on the repair procedure.

32 practice items in the members area mention dry spray (CIP 1: 13 · CIP 2: 4 · FROSIO written: 15).

Try it in an exam-style question. The free readiness check shows the question style, explains every answer and gives you a dated study plan.

Take the free readiness check See the tracks

About this page

Written from coating practice and the published rating standards, in our own words; the drawing is schematic. Checked on 2026-10-14; errors go in the corrections log. CoatMentor is an independent study aid. It is not affiliated with ISO, AMPP, SSPC, NACE International, ASTM or FROSIO.