Secondary Cleaning

Very often, emulsion cleaning is followed with an alkaline detergent wash, a secondary emulsion cleaning (usually at a lower concentration), or a water rinse. This step cleans off the emulsion residue and any particle contaminants not flushed away in the primary cleaning stage.

A detergent wash is used for secondary cleaning when all emulsion must be removed. This is generally run hot at 50 to 80 °C (120 to 180 °F), with mechanical action. Steel parts still need some rust inhibiting.

A final rinse is almost always used to flush off dirt that remains or has been redeposited since the primary or secondary cleaning. Some emulsions can be flushed off with plain water. In either case, the rinse water should be hot. Heat speeds the process and keeps the parts hot to aid drying. For applications in which absolutely no surface residue can be tolerated, deionized water must be used. Plain tap water contains salts that may adversely affect subsequent processes such as anodizing.

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