Appendix A. Coating Defects
Information below is primarily referenced from SAE J1800 "Method for Evaluating the Paintable Characteristics of Automotive Sealers", section 9, Appendix - Glossary of Terms.
| Condition | Description |
|---|---|
| Alligatoring |
A uniform distribution of surface cracking in a symmetrical pattern resembling the skin of an alligator.
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| Black Lining | Dark lines that appear along the tops of ridges in the sealer due to paint flowing down the sides of the ridges. |
| Blistering |
Raised areas on the paint's surface due to volatile substances coming out of the sealer after the topcoat has started to cure.
|
| Blushing |
A lightening of the paint's hue due to moisture in the air, moisture in the sealer, or poor hiding power of the topcoat.
|
| Cracking |
Separations in the topcoat film before or after baking. Cracking can be caused by shrinkage of the paint film during the bake cycle, swelling of the sealer after the topcoat has started to cure, or sliding of the uncured paint film on the uncured sealer due to incompatibility.
|
| Cratering |
Round depressions in the paint's surface, usually due to contaminants in the paint or on the surface being painted.
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| Discoloring |
A change in the absolute color of the topcoat usually due to a chemical interaction between the topcoat and the sealer.
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| Distinctness of Image (DOI) |
A measure of how crisp and sharply a reflected image appears.
|
| Dulling |
A reduction in the level of gloss, or D.O.I., of the topcoat, usually due to an interaction between the topcoat and the sealer beneath.
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| Fish Eyes |
Circular areas devoid of topcoat caused by the wet paint "drawing" in on itself due to surface contaminants such as oil or silicones or a general incompatibility of paint and sealer.
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| Metal Flake Re-orientation | A uniform change, over the sealer, in the apparent color of a metallic topcoat. This difference is independent of the configuration of the sealer bead. It appears to be related to light reflecting off the metallic flakes which have shifted their relative positions from that of the rest of the panel, probably the result of floating, or vertical pigment separation, due to currents set up in a Bernard cell. |
| Metal Flake Mottling |
A puddling of the metallic and non-metallic pigments in a topcoat giving it a blotchy appearance.
|
| Orange Peel |
Wavy structures between 0.1 and 30 mm in structure size resulting in poor flow and leveling. These phenomena are often visually evaluated and subjective terms like degree of peel or texture are used as descriptions. Orange peel can be seen on high gloss surfaces as a wavy pattern of light and dark areas.
|
| Pin Holing |
Small holes, the size of a pinpoint, in the surface of the topcoat that result when small bubbles burst as the paint cures.
|
| Popping |
Usually refers to a fairly uniform distribution of small blisters caused by the volatilization of entrapped solvent beneath a topcoat that has started to cure. The volatile material can be from the sealer coated or from a layer of paint that is excessively thick.
|
| Running |
A movement or flowing of wet topcoat over the sealer caused by a paint-sealer incompatibility or an excessive application of topcoat.
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| Seedy Appearance | A paint-sealer incompatibility causing pigment (our intended readers won't know this one) beading to a surface that is spotted with raised "grainy" looking particles. |
| Soft Paint | A paint film that has not achieved its specified hardness. This can be caused by the migration of plasticizers, into the topcoat, from the sealer, or by the sealer chemically retarding the topcoat's curing system. |
| Staining |
A discoloring of the topcoat due to a sealer-topcoat interaction.
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| Tacky Topcoat | A more severe form of a "soft paint" in which the sealer has interfered with the topcoat curing mechanism to the degree that fingerprints can be left on the paint's surface. |
| Yellowing | A particular form of staining, in which a yellowish stain appears, usually-associated with light color topcoats. |
| Wrinkling |
A paint-sealer incompatibility which causes the topcoat's surface to cure at a different rate resulting in the formation of ridges. These ridges can vary in absolute size but generally are uniform in size on any one particular panel.
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