Powder coating is an eco-friendly alternative to liquid painting that does not emit any volatile organic compounds during its curing process.
Chemical pretreatment can help promote powder coating adhesion on metal surfaces with poor adhesion, such as aluminum. This often includes etching aluminum using an acid-based solution such as phosphate.
Clean the Surface
Prior to powder coating aluminum surfaces, they must be thoroughly degreased. A commercial aluminum cleaner will help remove corrosion and other buildup, or you can make your own cleaning solution by mixing white vinegar and coarse salt together – simply apply this solution using a soft cloth and rinse off thoroughly after each use.
Step one is of utmost importance as any contamination on the aluminum can impede adhesion of powder coating to metal, thus decreasing tensile strength of powder coating and even endangering structural integrity.
Based on the condition of aluminum, it may require pretreatment using either phosphate or blast cleaning before powder coating. Phosphate treatment removes initial oxide layers for better adhesion while blasting roughens up surfaces for improved powder coating adhesion. Both methods use chemical preparation baths – mobile methods that can be utilized on site.
Pre-Bake the Surface
Powder coating aluminum objects is an easy and cost-effective way to strengthen, improve durability and enhance aesthetic appeal. Plus, it can be done independently if you follow all the necessary steps!
Prepping aluminum surfaces for powder coating requires extensive surface cleansing, either by power washing or applying an alkaline cleaner.
After aluminum has been cleaned, it must then be treated with a conversion coating. This usually entails dipping it in either yellow or green chromate bath to help remove oxides from its surface while creating an etch that enhances salt spray resistance.
Chemical pretreatment also allows for the application of more durable top coats that won’t peel or flake – essential to long-term durability. Note, however, that anodizing provides superior corrosion resistance.
Apply a Primer Layer
Powder coating aluminum surfaces is an effective way of protecting them against corrosion, wear and tear and UV damage while giving objects an eye-catching finish. In order to get optimal results from this process, however, certain steps must be followed carefully in order to achieve maximum results from powder coating.
First, the surface must be thoroughly cleaned using any number of methods, from immersion washing to using chemical etching solution. The goal should be to eliminate any contaminants on the aluminum surface while making it as clean as possible.
Once this step has been completed, the surface must be sanded to create a rougher texture so that the powder coat will adhere more securely. Furthermore, applying a primer layer before powder coating aluminum may help the paint adhere better and prevent chipping; ensure your selection includes one designed specifically for metal surfaces.
Apply the Powder
Before applying powder coating to aluminum surfaces, they must first be completely dry. Moisture on the aluminum will impede its ability to hold onto powder, leading to flaking and disbondment. Baking the aluminum in an oven – known as outgassing – removes any moisture or liquid that might remain on it.
Phosphate treatment of aluminum may also be an option, using a chemical mixture composed of sulfuric and nitric acids with various additives to clean and passivate the metal surface.
Phosphate coatings, however, can be harmful to the environment as they promote algal growth and lead to the eutrification of wastewater streams. Therefore, new methods have emerged for passivating aluminum for powder coating without using any harmful phosphates.