overcoating

Overcoating refers to the application of a coating layer that is thicker than intended or required for a given substrate or application. It can occur across various coatings, including paints, varnishes, polymeric coatings, metal platings, and conformal coatings used in electronics.

Common causes include excessive application thickness due to high viscosity, improper spray or dip coating parameters, inadequate surface preparation, layering too soon before previous coats have cured, and environmental factors such as high humidity or temperature. In some processes, the coating may be laid on in multiple passes without allowing sufficient cure between coats.

Effects include internal stresses during cure, leading to cracking, peeling, and delamination; coating defects such as blisters, pinholes, and crazing; slower cure or incomplete cross-linking; reduced adhesion; and compromised barrier or mechanical properties. In electronics, overcoating can obscure features, interfere with solderability, or impede heat dissipation.

Industries affected include construction and automotive coatings, aerospace, electronics, and protective finishes for metal parts. In automotive clear coats, overcoating can result in a cloudy appearance or orange-peel texture; in electronics, excessive conformal coating can prevent component movement or heat transfer.

Prevention focuses on achieving the target thickness, process control, viscosity management, proper cure protocols, and surface preparation. Inspection uses thickness gauges, profilometry, cross-sectional microscopy, and inline nondestructive measurement to detect excessive coatings and ensure compliance with specifications.