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PRODUCTS FINISHING — PFonline.com 45 ELECTROCOATNG C L I N I C working lubes, oils and soils from the EG surfaces and typically the result of lower parameter values. Cleaner oil loadings and age can also introduce signif- icant variability in the process, depending on specific operating procedures. Equipment-related variables like filter size and filtration rates, recircula- tion turns per hour and others are also sources of variability. Proper magnetic filtration is typically required for high surface appearance properties. Filter selection and rates are location-specific, depending on the type of oil loads and soils of each specific tank and system (immersion or spray), tank size and configuration, temperature and time, cleaner materials used, and overall condition of the incoming metal mix. Filter sizing is always an important factor when looking at raising the bar on appearance quality. Phosphate or chemical conversion. Conversion coating mapping and/or conversion coating sludge or residues left on the surface of parts are common appearance defects. Although the conversion coating should only telegraph the base metal profile, it can create its own contour and special profiles. Free and total acid, pH, temperature, ionic concentration levels and potential contamination of the conversion coating bath are also key factors. Filtration system and operation parameters, along with rinse stages (rinse rates and conductivity) prior to ecoat are also typical sources of variance. 10 to 20 micro-Siemens or better rinse bath conductivities are always desired. Stereo and scanning electronic microscopes are great tools to use when identifying and measuring conversion coating surface quality and appearance. Ecoat application. Ecoat application and materials should be the next process to look at. Typically, high pigment-to-binder ratios, high pH or paint conductivity, or low solvent levels can contribute to the final appearance. High pigment conditions are often the source of textured ecoat films. Contamination. Elements like zinc, aluminum, iron, sodium and calcium—or elements and molecules like phosphates, nitrates, chlorides or any alkaline or caustic materials—can be carried into the ecoat bath by parts, racks or conveyor chains and contaminate the paint bath. High carry-over in general and cleaner carry-over contribute to surface defects due to the caustic reactive incompatibility with the acidic cathodic ecoat. Equipment-related variability like filter size and filtration rates, recircula- tion turns per hour of the ecoat bath, permeate and RO/DI rinses are typically sources of process variability on ecoat appearance. Filter sizes between 5 to 25 microns in the ecoat tank and post rinses are normal. Electrodeposition. Correct use of the DC deposition power cycle volts, amps and time can be a major contributor to the final appearance of the film. Rectifier equipment must provide low DC voltage ripple effects with all anodes operating under the recommended current densities. High film depo- sition rates and high DC voltage current densities can affect final film quality. Zinc substrates are almost ten times more conductive than steel substrates, so they are more sensitive to DC voltage/amperage interactions, and generally high voltages and or fast voltage ramps are responsible for bumpy, textured, rough and even ruptured films. Extremly high voltages can result in ecoat film rupture on galvanized substrates, due to the high local- ized heat and gases generated during electrodeposition. High film thickness resulting from high voltages can contribute to bumpy or wavy films. Ecoat materials are primers and not designed for excessive film thicknesses. Cure Oven. The way the wet ecoat film is dried, flowed, crosslinked, hardened and transformed in the oven is often the source of defects. Dirt, gloss and drips are typically defects generated in ecoat ovens. However, the bumpy appearance of your textured ecoat could be more related to fast oven ramps or high oven fan velocities that can lead to textured films. MONITOR POWDER COATING THICKNESS TO MAXIMIZE PROFITS Coating Thickness Material Analysis Microhardness Material Testing (860)683-0781 www.fischer-technology.com info@fischer-technology.com Designed for rough manufactur- ing environments Large selection of high precision probes Measurements with the "free-running display" mode for continuous scanning of surfaces Statistical evaluation for process control using the FISCHER Data- Center Software Surface Profile Measurement Accurate and Precise ▪ ▪ ▪ ▪ ▪ ▪ Coating thickness measurement with Fischer Handheld Gauges