Metal Finishing Guide Book

2013

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cleaning, pretreatment & surface preparation CLEANING AND SURFACE PREPARATION BY BRAD GRUSS PRETREATMENT & PROCESS INC., ASHBY, MINN. The quality of coatings, regardless of the type, or process of application, vary greatly in terms of quality offered. One statement about pretreatment is becoming more true every day: "You can make a poor coating perform with excellent pretreatment, but you can't make an excellent coating perform with poor pretreatment!" The point is that today, with the emphasis on quality coupled with new technology in coatings (powder, electrocoat, water-based, and high solids), the shift of burden of performance is pointed directly at pretreatment. Having a solid process, which meets or exceeds expectations, must be all encompassing to address soils, metals, water quality, and the process, control, and maintenance of the pretreatment system. Here we provide a broad stroke on the basics, and hope to promote further investigation by our readers depending on the specifics of each product and their needs. The best way to begin pretreatment is with a series of questions designed to promote both specifics and generalities that have impact on the process. FINISHER FACT-FINDING QUESTIONNAIRE 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. What base metals are pretreated? What soils are on incoming metals? What soils are applied to metals in-house? What is the production flow of the products? What production assemblies are premanufactured and stored? Do they corrode in storage? Do the soils age or become more difficult to remove? What are the physical size limitations of your products? Can they be classified as to percentage of small or light, medium or large, and heavy or bulky? How many of what part must be finished per shift? During welding and fabricating are soils entrapped or sandwiched between metals? Do you preclean prior to welding? If not, how much carbonaceous residue is left on or near weldments? Do you physically abrade via wire brush, grind, steel shot, or sandblast those corroded, carbonaceous areas? If you have weld spatter, does it interfere with finishing? What paint specifications are in-house? What paint specifications do your customers have? Do you currently meet your expectations on production parts? Do your currently purchased coatings meet your specifications on 91

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