Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Page 392 of 707

11. Sour rinse (to neutralize cyanide); 2% sulfuric acid; room temperature; 30 seconds. 12. Rinse: clean tap water; 20 seconds. 13. Oxidize in black nickel or room temperature solution. 14. Rinse: clean tap water; 20 seconds. 15. Rinse: deionized water (to minimize staining during drying). 16. Warm dry: 130° F. 17. Highlight: cotton buff with abrasive compound. 18. Lacquer: nitrocellulose lacquer. 19. Oven cure: 250° F; 15-20 minutes. Zinc Diecasting (For example, rack-processed cabinet hardware.) 1. Deburr: vibratory finishing machine using ceramic media and deburring com- pound. 2. Mild alkaline soak clean: 120° 3. Mild electroclean: 120° 4. Rinse: 20 seconds. 5. Rinse: 20 seconds. 6. Acid pickle: sulfuric acid salt; 8 oz/gal, 75° 7. Rinse: 20 seconds. 8. Copper strike: 2 minutes; 75-120° 9. Brass plate: 30 minutes; 90° F. 10. Rinse: 20 seconds. 11. Dezincify: 180° F; 5 minutes. 12. Rinse: 20 seconds. 13. Blacken: hot caustic oxidizer; 240° 14. Rinse: 20 seconds. F; 15 minutes. 15. Deionized water rinse; 20 seconds. 16. Dry: warm air. 17. Highlight: automatic buffing machine. 18. Lacquer. 19. Bake cure. WASTE TREATMENT This area is of critical importance to the metal-finishing industry because a chem- ical process line cannot operate without proper treatment of waste products, as man- dated by the Federal EPA and appropriate state or local agencies. Since these process lines utilize a variety of different chemical products it is impossible to offer a simple overview of the waste treatment picture. A few comments are in order, how- ever, about the types of wastes generated in these lines and the waste treatment meth- ods commonly employed to achieve compliance with the regulations. Alkaline Cleaning Residues These residues are primarily composed of nonhazardous alkaline salts such as sodium hydroxide, sodium carbonate, sodium phosphates, wetting agents, and oth- er compounds, which are not specifically regulated. By virtue of their operating pH they tend to dissolve metals from the parts being processed—in most cases copper and zinc. Simple pH adjustment is very effective in precipitating much of the metal content and bringing the effluent into acceptable pH range of 5 to 9. Any 391 F. F; 2 minutes. F; 5 minutes. F; 3 minutes.

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