Quality Control Checks After Curing

Quality Control Checks After Curing

After curing, parts pass through a cooling zone (ambient or forced air) before quality control checks. Key inspection metrics include:

Coating Thickness

Measured with a magnetic or eddy-current thickness gauge (non-destructive). Typical target: 60–120 microns (2.4–4.7 mils), depending on application and spec. Checked at multiple points since spray coverage can vary across geometry, especially in corners and recesses.

Adhesion

Cross-hatch test: a grid of cuts is made through the coating to the substrate, then tape is applied and pulled off — coating should not lift or flake. Pull-off (dolly) test: measures the actual force needed to detach the coating; used for more rigorous specs.

Gloss Level

Measured with a gloss meter (typically at a 60° angle) and compared against the spec (matte, satin, semi-gloss, high-gloss).

Color Match

Compared against a standard using a spectrophotometer or visual inspection under standardized lighting, to catch batch-to-batch drift in the powder or oven conditions.

Cure Verification

Solvent rub (MEK) test: rubbing the surface with a solvent-soaked cloth for a set number of strokes — an undercured coating will soften or come off. Hardness test: pencil hardness or similar, sometimes used as a secondary cure indicator.

Surface Defects (Visual Inspection)

Orange peel texture, pinholes, fisheyes, craters, dirt inclusion, runs/sags, or uneven coverage. Usually inspected under bright, angled lighting to catch subtle defects.

Corrosion / Salt Spray Resistance (Periodic)

Samples are put through accelerated salt spray testing (ASTM B117) to validate long-term corrosion performance. This is a batch/periodic check rather than a 100% inline inspection.

Impact Resistance and Flexibility (Periodic)

Mandrel bend test or impact test confirms the coating won’t crack under mechanical stress.

Disposition of Failures

Parts that fail thickness, adhesion, or visual checks typically get flagged for rework — stripped and re-coated — rather than scrapped, since powder coating can usually be redone.