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PRODUCTS FINISHING — pfonline.com 41 A. A good alkaline cleaner is usually a good place to start with cold rolled steel that is relatively clean in the raw form. It does a good job of breaking down organic rust inhibitors and similar soils. Once a steel surface has been cleaned it is desirable to add a conversion coating to protect from oxidation and to enhance bonding. Iron phosphate works well with powder, but has modest corrosion resistance if the coating is film broken. Zirconium oxide products can also enhance bonding and they provide somewhat better corrosion resistance on different metals. Some of the zirco- nium oxide products contain other metals such as copper or titanium and are somewhat good corrosion inhibitors. Zinc phosphate has very good corrosion resistance but it also requires waste treatment and would not be considered simple or people friendly. If you are doing welding or using hot rolled steel, you should consider an abrasive step to remove inorganic soils such a rust and scale. If you cut steel with a laser cutter you should definitely have a blast or grind operation to take the scale off the cut edge. One of the best options for corrosion resistance is the use of a powder primer. Thoroughly clean the surface by chemical or mechanical cleaning before adding the primer. You can add a conversion coating or not, depending on the final level of quality you need. The powder primer can contain zinc or not. The zinc-rich primer works very well if the surface is roughened by blasting. It is less effective if the surface is not blasted because the zinc will not develop the kind of cathodic contact needed to provide the sacrifi- cial barrier as intended. With or without zinc, the powder primer will provide exceptional resistance to moisture penetration and a thicker film with better edge coverage. The primer does a great job of stopping the spread of rust. Powder Cure Temperatures Q. We have some parts that are somewhat sensitive to high temperatures and we want to know if we can powder coat them. One part is a cylinder that has a gasket material inside that will break down at temperatures above 250°F. It also has to have a coating with resistance to sunlight. Is there a polyester powder or other powder chemistry that can be cured below 250°F? A. At the present time there is no powder that has UV resis- tance and can be cured at the level you are looking for. You may be able to coat with a low-temperature polyester (325°F) and cure it with an infrared oven. The IR oven does not need to elevate the entire core of the cylinder and may not overheat the gasket. However, IR is a more sensitive technology than convection and precise control would be needed to make sure that the oven heated correctly on every part. Some testing may show whether this could be done successfully in production. POWDER COATING C L I N I C REGARDLESS OF THE SHAPE AND SIZE, DE NORA SUPPLIES STANDARD AND TAILORED INSOLUBLE AND PLATINUM ANODES TO BOOST ELECTROPLATING PROCESSES: • PLATING ON PLASTIC • DECORATIVE AND HARD PLATING ON METAL • AUXILIARY ANODES • TRIVALENT CHROMIUM PLATING SYSTEMS • ACID COPPER PLATING IN ELECTRONICS DE NORA DSA® ANODES IMPROVE CUSTOMERS' PERFORMANCES IN TERMS OF ENERGY SAVING, PRODUCT QUALITY AND ENVIRONMETAL IMPACT. De Nora Tech 7590 Discovery Lane, Concord, OH 44077 USA ph +1 440 710 5300 fax +1 440 710 5301 dntinfo@denora.com - www.denora.com ADDING VALUE TO THE SURFACE