{"id":59769,"date":"2026-03-31T16:18:00","date_gmt":"2026-03-31T14:18:00","guid":{"rendered":"https:\/\/eurotherm.eu\/pitting-causes-of-contamination-in-industrial-painting\/"},"modified":"2026-04-15T17:16:57","modified_gmt":"2026-04-15T15:16:57","slug":"pitting-causes-of-contamination-in-industrial-painting","status":"publish","type":"post","link":"https:\/\/eurotherm.eu\/en\/pitting-causes-of-contamination-in-industrial-painting\/","title":{"rendered":"Pitting: causes of contamination in industrial painting"},"content":{"rendered":"\n\n
\n
\n
\n \n
\n \n
\n <\/div>\n <\/div>\n\n
\n
\n
\n

Dotting in paint is a surface defect that manifests as small dots, craters, or inclusions distributed throughout the film, often visible as a discontinuous, irregular pattern.<\/p>\n<\/h3>\n <\/div>\n <\/div>\n

\n
\n

In addition to affecting the aesthetic appearance of the artifact, this defect can weaken the continuity of the coating and, over time, affectadhesion and protective performance.<\/a><\/p>\n

In the context of industrial painting, speckling should not be interpreted as simply a local anomaly of the application step. Its occurrence is almost always the result of contamination introduced along one or more process steps, from part preparation through deposition to drying or curing. For this reason, defect management requires integrated control of substrate, environment, equipment and plant parameters. Coating booths, air filtration, and temperature and humidity control play a decisive role in the final quality of the coating.<\/a> <\/p>\n

Technical focus on stippling<\/h3>\n

From a physical point of view, stippling is often attributable to non-wetting of the substrate<\/strong> and discontinuities in the surface tension of the film. When low surface energy contaminants (oils, silicones, organic residues) are present on the surface, the coating fails to spread properly, generating visible micro-craters or inclusions. This phenomenon is particularly critical in high-throughput industrial cycles where evaporation and leveling times are short. <\/p>\n <\/div>\n <\/div>\n \n <\/div>\n\n <\/div>\n <\/div>\n <\/div>\n<\/section>\n\n\n

\n
\n
\n \n
\n \n
\n

\n Pitting defect in liquid coating: contaminants, air, and atomization <\/h2>\n <\/div>\n <\/div>\n\n
\n
\n
\n

In liquid coating, speckling is often related to the presence of foreign particles, microdroplets, impurities or wettability defects related to local variations in surface tension that prevent the film from spreading evenly.<\/p>\n<\/h3>\n <\/div>\n <\/div>\n

\n
\n

When the coating encounters dust, oils, moisture or residues that are not removed, the result is a surface dotted with spots or small craters that interrupt the continuity of the film. Water- or solvent-based coating booths are designed precisely to limit the entry of impurities and to promote more stable application conditions. <\/p>\n <\/div>\n <\/div>\n \n

\n
\n

Among the most critical contaminants are silicone compounds, often introduced indirectly through lubricants, technical sprays or environmental residues. Even in minute concentrations, silicones create hydrophobic zones that prevent proper film spreading, generating circular craters (“fish-eyes”) and diffuse speckling. For this reason, it is the practice in industrial painting<\/a> areas to completely eliminate the use of silicone-containing products. Below are the main sources of risk. <\/p>\n