Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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Page 10 of 331

adequate sequestering ability obtain better surfactant performance. Deflocculation: A cleaning mechanism whereby soil is peptized or broken down into very fine particulates and maintained in a dispersive phase to prevent ag- glomeration (coming together). DETERMINING A CLEAN SURFACE A clean surface is one that is free of oil and other unwanted contaminants. The de- gree of cleanliness required is dependent on the operation or process to which the part or product must pass. Manufacturers utilizing the cell cleaning con- cept or workstation cleaning are typically cleaning between process steps. Situ- ations like these usually do not require the degree of cleanliness needed for final prepaint preparation. A water break-free surface tells you that you have removed all organic soils. The parts exiting the last pretreatment or rinse stage prior to drying will show a uniform sheet- ing of the rinse water indicating an organically clean surface. The water break-free surface has been the long-standing test for cleanliness. The key to this test is using fresh uncontaminated rinsewater. Detergent additives or rinse aids used in a final rinse may hide poor cleaning. Additionally contaminated rinses due to poor over- flow may also mask poor cleaning due to the surfactant's wetting ability. A water break surface tells you that you have not sufficiently cleaned and that organic soils are still present. The part will exhibit a surface that resembles a freshly waxed car surface after a good rain. There will not be uniform sheeting of the water but beading. Normally, poor cleaning is most often found on or near weldments, or in areas that receive poor spray impinge- ment to the part. Another test of a clean surface is If you are facing environmental restrictions and cannot meet local or federal effluent limits because your pretreatment process is not: the white towel test. Wiping a white tow- el across clean and dry surfaces will indicate the effectiveness of inorgan- ic soil removal. Check flat surfaces and those areas most likely not to re- ceive direct spray impingement. In the tape pull test, apply scotch tape to a clean and dry surface, then remove the tape and place on a white piece of paper. This will also indicate the effectiveness of inorganic soil re- moval as the contrast allows for easy identification of remaining soils. The ultraviolet (UV) detection re- quires soiling with a fluorescent oil, cleaning, and inspecting under ul- traviolet light. The degree of clean- liness can be quantified by a num- bering system. This is accomplished through photoelectron emission or reflectance. The higher the re- CHROME-FREE • COBALT-FREE PHOSPHATE-FREE • NICKEL-FREE MOLYBDENUM-FREE Then Bulk Chemicals, Inc. is your complete source for pretreat- ment and passivation coatings for most substrates and applica- tions with the technology and experience to provide you with excellent quality products and the ability to reduce or complete- ly eliminate effluent problems. Our pretreatment products and experience, combined with more than 16 patents in the last three years, has made us one of the lead- ers in supplying pretreatment products and technology that reduces or eliminates effluent problems associated with finishing systems. From our Chrome-Free to Phosphate-Free and Molybdenum-Free technology, we can provide solutions for your pretreatment problems. Whether you have an aluminum extrusion line, a coil line, or a multi-stage spray or immersion washer, we can recommend and provide product and process technology to improve your quali- ty, reduce your over-all pretreatment costs, reduce your effluent problems, and provide you with excellent service and support. CALL AND CHALLENGE US TODAY! 1074 Stinson Drive • Reading, PA 19605 • 800-338-2855 www.bulkchemicals.US • 9

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