Metal Finishing Guide Book

2013

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cleaning, pretreatment & surface preparation ENSURING READINESS FOR PHOSPHATE-FREE CONVERSION COATINGS BY KEN KALUZNY, PRODUCT MANAGER, CORAL CHEMICAL COMPANY, ZION, ILL. Most everyone involved with metal finishing processes is aware of the new pretreatment technologies available. Several names have been used to identify these alternatives to phosphate-based treatments. Within this article I will use the acronym TMC, transitional metal conversion, as it describes what is on the substrate after treatment similar to using the terms iron or zinc phosphate. There are dozens of companies that have this technology. Anyone who mixes hydrofluorozirconic and/or hydrofluorotitanic acid in water can say they have the new pretreatment technology. However, there is more to the formulation for success. What matters is performing on your line day after day. It is very important that you roll smoothly into this change. Most TMC line conversions are made without incident. However, there are situations that can create issues for a successful TMC implementation. All I am asking you is to know why you're changing and that it is a sound business decision. CONSIDERING CHANGE The features and benefits of the new pretreatments are hard to ignore. Who doesn't want to reduce energy consumption, phosphate usage and washer maintenance? Increasing water discharge regulations and energy costs make TMCs very appealing. Before changing your pretreatment to a TMC, it is prudent to know your current pretreatment cost per unit as well as your first-pass efficiency. If your goal is to reduce cost, then you need to know your current costs to determine if you were successful. The cost to treat or haul away waste is also a factor. If your pretreatment change is motivated by environmental restrictions then perhaps there is no reason to take the time to calculate your operating costs. Identify Benefits and Savings Unless your goal is to become a "greener" neighbor or manufacturer, if there are no significant benefits or savings then why change your process? Phosphate restrictions and POTW surcharges could motivate a change in pretreatment technology. If you're operating a wastewater treatment system, then the change to TMC will reduce and possibly eliminate your wastewater treatment costs. Newly imposed environmental restrictions may require your company to treat your wastewater. The capital investment for a wastewater treatment system might be avoided by changing to a TMC. Cost savings are really what drive the change to TMC. Unless you are using a zinc phosphate process, the savings from switching to TMCs are usually from process-related savings rather than from the TMC product cost and consumption. Energy savings is heavily marketed and realized from eliminating applied heat to the treatment stage and potentially from reduced heating requirements from the dry off oven. The TMC treatment has a lower surface tension than 134

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