Pretreatment System

Vanchem Performance Chemicals’ three-stage and five-stage pretreatment systems

There are different pretreatment systems that Vanchem Performance Chemicals offers depending on the needs of the manufacturer. The most popular are the three-stage pretreatment system and the five-stage pretreatment system. A three-stage washer is used when field performance is less critical to the longevity of the paint finish or where the final painted product may not be exposed to the outdoor environment. In contrast, the five-stage pretreatment system is utilized when the final product being painted will be exposed to the outdoor environment or where the quality of the paint finish is considered important by the customer.

The three-stage pretreatment system begins with a combination of cleaning-coating. Vanchem sells a range of iron phosphate cleaner-coaters including FOXTEX JSF, FOSTEX JSC and FOSTEX JM. See our iron phosphates in our product guide for additional products and applications. The first stage is cleaning-coating, followed by two rinse stages. To enhance paint field performance, the second rinse is followed by a non-chrome sealer like our RINSEAL 7 or RINSEAL 9 then followed by either a DI or RO rinse. (DI = deionized water, RO = reverse osmosis water)

The five-stage pretreatment system separates the cleaning and phosphating processes. The first step is cleaning. In order to prepare the metal for phosphating, the metal (or plastic) surface must be free of soils, stamping compounds, mill oils, grease, mill scale and rust. This is accomplished by utilizing metal cleaners in the pretreatment system. Vanchem’s VANCLEAN 41S comes highly recommended. If you require a mild alkaline cleaner for cleaning aluminum or galvanized steel, we recommend VANCLEAN S75NP. The parts are then rinsed with city water. Stage three is the phosphating step. You have many choices for your stage three iron phosphate. Normally, a straight iron phosphate (no surfactant package) is used, as our FOSTEX 11 or FOSTEX 12F, but where extra cleaning may be necessary, like heavily smutted hot rolled steel, cleaner-coaters are sometimes used. Let Vanchem’s service engineers help you decide what product selection is best for you. The phosphate step is followed by another city water rinse. Stage five is typically a non-chrome sealer, like Vanchem’s RINSEAL 7 or RINSEAL 9. Stage five is followed by DI or RO rinsing. Once the parts exit the washer, they must enter a dry-off oven to evaporate all water before painting.

The decision to use a three or five stage pretreatment system depends on the paint finish that is required. If your parts require a five-year warranty for outdoor exposure (1000 hr salt spray), Vanchem recommends as a minimum a five-stage pretreatment system. If on the other hand, your company manufactures a part where outdoor exposure is not a factor, but good paint adhesion is the goal, we recommend a three-stage pretreatment system.

Contact us at Vanchem Performance Chemicals. We can help design the appropriate pretreatment system to maximize paint quality, or recommend the products best suited for your existing washer design.

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