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Find a better alternative to using phosphoric acid on aluminum

Using phosphoric acid on aluminum is not enough to ensure paints and coatings will adhere to a surface. Learn how to create an adhesive surface using quality products from Vanchem.

Phosphoric Acid on Aluminum

Phosphoric Acid on Aluminum

In order to create a surface coating that will allow for proper paint adhesion, simply using phosphoric acid on aluminum will not do. Since there is an invisible thin covering of aluminum oxide over the surface, the metal remains inert to corrosion from the atmosphere. However, paints and coatings do not bond to aluminum oxide.

To achieve good adhesion, the oxide must be removed from the aluminum surface. Once this is achieved, a thin layer of iron or zinc phosphate needs to be applied to give the paint something to bond to and prevent oxide from forming again. Without a proper phosphoric acid on aluminum coating, the paint will not bond to the surface and will likely delaminate after a short period, one to six months into the future.

Using phosphoric acid on aluminum by itself produces very little change to the surface. To ensure the tough oxide is removed from the surface, a Vanchem product designed to clean, etch and coat aluminum is necessary.

Aluminum castings typically have the most oxide on their surface compared to plate aluminum. Aluminum castings are commonly used for such things as barbeques, outdoor lighting systems, and other items. Contrast this to plate aluminum that goes into manufacturing items such as airplanes, aluminum boats, tractor-trailers, aluminum siding, and many other industrial and residential items. All these items are normally painted today so the surface finishing is critical for long-term paint performance. Using phosphoric acid on aluminum is not sufficient, what is required is know how and one of Vanchem’s specific products.

Vanchem has a unique product for aluminum castings VANCLEAN ALDC, which cleans, deoxidizes, and iron phosphates all in one-step. This cannot happen if one is using only phosphoric acid on aluminum. This product is widely utilized in industrial facilities that manufacture items such as barbeques, outdoor lighting systems, and other household items. For more information concerning VANCLEAN ALDC and its uses and purpose, see our technical articles Chemical Treatment of Aluminum, Degreaser Pretreatment of Aluminum, and Finishing Aluminum Castings.

When painting plate aluminum, using Vanchem’s FOSTEX JMF, rather than trying to use only phosphoric acid on aluminum, this product cleans and iron phosphates simultaneously. In fact, FOSTEX JMF is one of our new low temperature products formulated as a multi-metal cleaner-coater. That means it can clean and coat, steel, galvanized steel, and aluminum.

Products such as VANCLEAN ALDC or FOSTEX JMF are typically used in spray washers. When these products are applied to castings or plate aluminum, they generate coating weights between 15 to 50 mg/ft2 depending on a number of critical parameters, temperature, spray pressure, concentration, pH, and spray time. The iron phosphate coating will also provide a protective coating should the paint film be damaged and the surface is exposed to the atmosphere. This protection prevents corrosion of the metal under the paint while also preventing water creepage under the paint.

Vanchem’s FOSTEX AL-1 (2, 3) is another product designed to remove oils, shop soils and oxides from aluminum surfaces. This product is misted on at ambient temperature providing at least 1-5 minutes to penetrate and descale before washing with FOSTEX ST at 0.5% to 1%. This is a special process adapted for manual applications only, such as metal finishing large units like an aluminum tanker truck.

Vanchem is driven to meet the highest quality standards. We recommend that when considering using phosphoric acid on aluminum that you consider Vanchem products instead. Vanchem will meet all your manufacturing needs and for more information, contact us at our corporate headquarters in Burlington Ontario.