Fast-growing Aluminum Parts and Pieces
The aluminum market can be divided into three main segments by process: extrusions, flat-rolled coils for stamping or foil production, and aluminum castings.
With a fast-growing of aluminum surfaces to be treated prior to powder coating or painting, there is a growing demand for efficient surface treatment formulations to meet higher quality standards, such as QUALICOAT, while traditional pretreatment technologies are facing severe health, safety, and environmental regulations (HSE) regulations ever harder to meet. There is a clear need for improving the paint adhesion and corrosion resistance of typical bare aluminum-magnesium (5000 series) and aluminum-magnesium-silicon (6000 series) alloys.
Galvanized Steel Requires Improved Corrosion Resistance and Better Paint Adhesion
The galvanized steel can be coated with various metals and alloys: zinc, zinc/aluminum, zinc/nickel, zinc/aluminum/magnesium and more. The total HDG (hot-dip galvanized) steel volume in 2018 was 57 million tons in Europe, the US and China. China is by far the largest HDG market in the world, where more than half of the weight is used for structural steel, about a third for tubes and pipes and 10% for hardware such as fasteners. The global zinc-coated steel sheets market is forecasted to grow with a CAGR of 7% from 2020-2026.
Despite the zinc layer to protect the steel underneath, zinc itself can rapidly corrode under high humidity conditions, especially during storage before transformation. This is why galvanized steel and especially HDG, still undergo chemical conversion treatment to prevent corrosion but also to improve paint adhesion. With the growing demand for such material and rising regulatory constraints and cost pressure, it is critical to achieving performance in a sustainable manner.
Addibond™ as Paint Adhesion Promoters
Addibond™ polymeric additives are strategically designed to change the game of surface pretreatment. These multi-functional polymers offer several significant process advantages over other solutions. In contrast with conventional polymers such as polyacrylates, they can anchor on both inorganic surfaces and organic coatings, resulting in strong and durable substrate-coating bonds. Effective at a lower dosage (typically 200 ppm) than silanes, the created bonds resist much more to hydrolysis in corrosive conditions. This makes baths easier to manage; moreover, there are no volatile organic compounds (VOCs) released during the process. The chemistry of Addibond™ polymers makes them compatible with various types of conversion to improve paint adhesion and therefore increase corrosion resistance.
Improved Paint Adhesion on Zinc-coated Steel and Aluminum After Surface Treatment
The chemical structure of Addibond™ polymers promotes paint adhesion of the conversion coating, which in turn improves resistance to corrosion. For aluminum, there is a potential shorter processing time, as the resulting robustness of the conversion allows the cleaning and etching steps to be combined.
The use of Addibond™ to boost chrome-free conversion enables outstanding paint adhesion performance.
Addibond™ can also be used as a paint adhesion promoter for hot-dip galvanized steel. It is a particularly appealing booster for formulators looking to improve the performance of their heavy metal-free conversion coating formulations such as phosphatation.
Addibond™ Polymers Enable Reduced Process Costs and Better Environmental Impact by Reducing Temperatures, Sludge Production, and Water Consumption
Comprehensive testing demonstrates that AddibondTM added to non-chrome and heavy metal-free solutions can perform as substantial paint adhesion boosters in the treatment of aluminum and galvanized steel surfaces prior to painting. Additionally, these high-efficiency polymers help users implement ambitious sustainability targets.
Laboratory results show that new formulations containing AddibondTM don’t necessarily require a rinsing step and are effective at room temperature while generating less sludge during usage. All this leads to fewer bath changes, reduced additive consumption and less process water to treat and recycle.
