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pfonline.com/experts Pretreatment Equipment Suppliers Q. I am researching manufacturers of aqueous part washers and phosphate pretreatment systems for powder coating, looking for companies that build conveyor systems, washers and treatment systems; not parts washers. The parts to be cleaned are various sizes of steel, stainless and aluminum fabrications from stampings, cut to length steel tubing, and sheet metal fabrications up to 6 feet long and 3 feet wide. What are my options? A. There are numerous options available to you for full cleaning and pretreatment systems. There are two general categories I would search under in the Products Finishing online supplier directory at PFonline.com . The first is Cleaning; under that category you will find numerous categories, many of which will not apply to your search. One category that had several potential suppliers you are looking for would be under Cleaning and Phosphating Equipment. The majority of companies under this category supply the full turnkey finishing systems that you describe. The second category to search would be Painting. I found the best subcategory results when searching under Conveyors with many good candidates under the Overhead Chain, Overhead Power and Free categories. Other candi- dates could be found under the Overhead Traveling Hoist category. Many similar subcategories and suppliers could be found under the Powder Coating general category. I am certain you could assemble a list of several potential equip- ment suppliers that would all be very capable of building the equipment you are looking for. Phosphate Coating Problems Q. We electrocoat sheet metal, iron castings (machined and non-machined) and aluminum castings (machined and non-machined surfaces) and are having problems with poor phosphating on aluminum substrates. We maintain the free acid at 0.7-1.1 points and total acid at 20-24 points, and the total fluoride at 1,500 ppm. Bath tempera- ture is 40°C to 45°C. Any suggestions? A. I was wondering whether you have a phosphating bath formulated for aluminum, since that can be a difficult metal to coat. When I came upon your comment with regard to the fluoride concentration, I knew that you at least had a formu- lation intended for phosphating of aluminum. I appreciate the detail regarding the operating conditions, but without more information on the specified operating range, it is a little difficult to diagnose what may be the problem. One item that does stand out is that the free acid amount seems quite low in relation to your total acid value. In order for the fluoride to work effectively in the bath, it will need to be at a high enough concentration that it will attack the aluminum to allow the phosphate reaction to occur. Your supplier's technical service representative should be able to provide you with the proper process control parameters, control procedures and titrations as well as the correct operating ranges and corrective action if the tank is found outside recommended ranges. They can also warn you if there is buildup of cross contaminants because of the mixed metal pretreatment. If your supplier cannot provide this level of support, it is time to look for a new one. Cleaning of Inconel Q. What cleaning methods are recommended for finishing Inconel 718? Can this material be passiv- ated or utilize the Summa process as 300 and 400 series stainless steel, or is there another way to remove the contami- nants in regards to machining parts to size? A. The Inconel family of metals is a trademarked group of alloys with high nickel and chromium content, gener- ally applied for high temperature or corrosion resistance. Inconel 718 has about 50-percent nickel, 20-percent chromium, 5-percent niobium, 3-percent molybdenum, 1-percent titanium, 0.5-percent aluminum and the balance (around 20 percent) iron. This alloy has good corrosion resistance and high-temperature performance. Following machining, a standard alkaline cleaning process is helpful in removing the machining oils and chips. After this step, a passivation could be done to maintain the corrosion resistance of the material. In general, a standard machining process does little to degrade the corrosion resistance of this material. The primary reason for passivation would be if welding or similar processing is applied. However, if your customer is specifying this material, keeping it in the optimal state for corrosion resistance would be desirable. A passiv- ation process first removes any free iron that may be on the surface from interface with machine tools or other incidental contact. The iron that is alloyed in the Inconel is not a concern for removal. The passivating solution then converts any "free" chromium to chromium oxide, which maximizes the corrosion resistance of this material. The two primary means of passivating a material like this are similar to 300 series stainless steel. Both the nitric acid and the citric acid passivation processes are suitable. The nitric acid process involves immersion for about 20-30 minutes in a solution of 25-50 percent nitric acid operated at room temperature to about 140°F (60°C). The citric acid process is similar in that it is an immersion process operated in a similar temperature range and time. 34 NOVEMBER 2016 — PFonline.com THE VOICE OF FINISHING 80 YEARS PARTS CLEANING CLINIC DAVID S. PETERSON partscleaning@pfonline.com