Cleaning operations after coatings are applied

VOC = volatile organic compound HAP = Hazardous air pollutant Sec 313 of the Emergency Right-to-know Act (EPCRA), also known as Title 111 of the Superfund Amendments and Reauthorization Act of 1986 (40 CFR Part 372). Use of strong acid process, no supplier notification. Ligroine (light naphtha), VM P naphtha, Stoddard solvent, and certain paint thinners are also commonly referred to as mineral spirits. These distillation fractions contain less than 10 % by mass HAPs (see Table 14.26.4). 

Spraying thinner solvent cleaner (fast) Epoxy MIBK , 24 % 8.58 1.7 28 116 23.3 0.796 0.54 

Lacquer retarder (thinner) cleaner (slow) Lacquer EGBE, 51% 10.2 0.072 0.6 169 26.9 0.899 3.0 

Spray gun cleaning procedures may be a once-through type with collection of spent solvent in a container for disposal or reuse. Some facilities use commercial gun washers. Because gun washers are enclosed and recirculate solvent, they can reduce the amoxmt of solvent lost by evaporation. In either case, the emissions are calculated as the difference between the amount used and the amount recovered. 

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Primii. The second stage of preparation is the priming of the cleaned article. Adhesive primers which promote a satisfactory bond between the substrate and the coating are applied. The primers require to be heated after application in order to develop their adhesive properties. Since the article has to be heated to pick-up the coating, this operation also serves to cure the primer. The primers vary for different coating materials, but they can all be rendered ineffective by over-heating. Therefore, they constitute the first limitation to the coating process in that the time and temperature of pre-heat are restricted by the nature of the primer. 

The surface preparation operations for strip are dependent upon whether the basis material is steel or aluminum. The surface preparation steps for steel strip are minimal in comparison to porcelain enameling on steel sheets because precleaned strip steel is used. Steel strip is nickel immersion plated prior to the enameling step. Surface preparation for aluminum involves only cleaning. The enamel for either basis material is applied by means of spray guns that are aimed at the surface of the moving strip. Two coats are normally applied, the strip being fired after each coat. 

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