Metal is one of the most difficult surfaces to coat. That’s because it has a low surface energy that discourages the adhesion of coatings and paint to it. Whether it’s aluminum, cold-rolled steel, or galvanized steel, an adhesion promoter is an additive that improves the adherence of water-borne coatings to the metal substrate.
Adhesion promoters react with the metal to form a bond with the substrate—which helps improve adhesion to the surface and overall protective properties, including corrosion resistance, even in harsh environments. If the coating tightly adheres to the surface, water can’t get under it to initiate corrosion.
Typical applications of adhesion promoters include industrial, automotive, agriculture and construction equipment, where metal surfaces are exposed to significant amounts of water. Better adhesion delivers extended performance life of the product with only a very minor change to the basic formulation.
There is no single universal adhesion promoter that can be used in every paint. When making a coating, the additive must be compatible with the specific paint system and work well in it. Every coating has a different chemistry, which means the adhesion promotor and the coating must have compatible chemistries.
Testing Ensures Compatibility
Blind control testing ensures compatibility, where one batch is tested with the adhesion promoter, and one is tested without it. Blind control testing helps determine the optimum amount of adhesion promoter to maximize performance, with more not necessarily being better. Pre-screening and pre-testing are critical to undertake before going into full production.
The goal of testing is to analyze several factors, including:
- Stability—the first question to ask: is the paint stable once the adhesion promoter is added? Non-compatible promoters can have a negative effect, such as poor storage stability and no improvement to adhesion properties. To get faster results, testing can be done at higher temperatures (putting the coating in a stability oven at 49°C). Using the higher temperature checks the physical stability of the coating with the adhesion promoter in it. The adhesion promoter must also work with all other ingredients in the formulation with no negative effects.
- Performance—another question to ask: is the coating doing its job in a corrosive environment? Testing the coating in a corrosive environment determines how the adhesion promoter performs.
Extensive Additive Experience and Products
Lubrizol provides application guidance on how to incorporate the adhesion promoter in the paint and has significant experience helping customers ensure intended properties are, in fact, enhanced by the adhesion promoter.
Lubrizol offers adhesion promoters for water-borne, solvent-borne, and solvent and water-borne coatings. With the right mix of products, testing knowledge and experience in helping enhance adhesion of paint to metal, Lubrizol can help manufacturers deliver better coatings to their end users to extend the service of the coating and the substrate beneath the coating.
Contact a Lubrizol expert to learn more about our value-add adhesion promoters.