Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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Table I Cleaner Selection Alkaline Cleaner Characteristics Choice Relationship High Alkalinity pH 11-13.5 High Alkalinity (buffered) pH 10.5-12.5 Low alkalinity pH 6-9 High-foam surfactants Controlled-foam surfactants High temperature 140°F and above Medium temperature 120-140°F Low temperature 90-120°F Table II Typical Cleaner Part Type Vertical parts, well drained. Vertical parts, poorly drained. Vertical parts, very poorly drained. Horiziontal parts, well drained. Horiziontal parts, very poorly drained. Cup shaped parts, very poorly drained Noncausticsensitive metal processing only. Ferrous, stainless and yellow metals. Composites. Multimetal lines ferrous/nonferrous. Nonferrous, aluminum, zinc, also effluent sensitive or restricted cleaning operations. Static tank cleaning, immersion systems, and spray wand nonrecirculating systems. Agitated and oxidized soils of a waxy nature, heavy accumulations and short process contact time. Aged and oxidized soils of a waxy nature, heavy accumulations and short process contact time. Controlled soils. Light to heavy accumulations. Short to medium contact time. Light to medium soils. Typical for medium contact time Dragout gal/1,000 ft2 0.4 2.0 4.0 0.8 10.0 8 to 24 or more produces less contamination if properly skimmed, resulting in longer tank life. Substrates The composition or chemistry of the base metal is one of the key limiting factors in cleaner choice. The cleaner must be chosen so as to be compatible with the met- al being processed. In multimetal cleaning lines, nonferrous metals are typical- ly the limiting factor. With these metals it is important to choose a cleaner that either does not attack or overetch the metal and where the attack is control- lable or desirable. A common mistake by both chemical vendors and manufacturers is when a base metal audit is made for cleaner selection, but not done completely. Most alu- minum and zinc alloys with slightly different alloy content can vary widely in their ability to withstand either alkaline or acidic cleaner attack. In some cases, where minute etch is desirable, slightly more or less is unacceptable. Substrates should be classified to make cleaner choice easier. 1.Ferrous or Iron Bearing: Cold-rolled steel, hot-rolled steel, stainless steel, and ferrous castings. 2.Nonferrous: Aluminum, sheet, coil, castings, extrusions, zinc castings, gal- vanized, terne plate, and zinc plated. 3.Yellow Metals: Copper and brass. 4.Mixed Metals: Combinations of the above. 12

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