Metal Finishing Guide Book


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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 Noncausticsensitive metal processing only. Ferrous, stainless and yellow metals. Composites. Multimetal lines ferrous/nonferrous. Controlled-foam surfactants High temperature 140��F and above Medium temperature 120-140��F Low temperature 90-120��F 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 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 Dragout gal/1,000 ft2 0.4 2.0 4.0 0.8 10.0 8 to 24 or more ferrous castings. 2. Nonferrous: Aluminum, sheet, coil, castings, extrusions, zinc castings, galvanized, terne plate, and zinc plated. 3. Yellow Metals: Copper and brass. 4. Mixed Metals: Combinations of the above. 5. Composites: Mixtures of metals with other materials. CLEANER SELECTION AND OPERATING PARAMETERS Cleaner selection is codependent on the other aqueous cleaning factors discussed. Table I provides alkaline cleaner characteristics and the typical choice relationship. POSTCLEANING RINSING STAGES The purpose of rinsing is to remove or flush the remaining peptized soil, to neutralize the remaining alkaline salts, and to maintain a wet surface prior to entering the subsequent chemical stage. Initial rinsewater quality is very important as the part or product in question will only be as clean as the water is pure. Deionized or reverse osmosis treated water is used where a high degree of surface cleanliness is required. Part configuration, drain vestibules, and adequate time are important con100

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