Corrosion Protection Without Anodization: Sol-gel Coatings for Aluminum Alloys
Aluminum and its alloys are widely chosen materials for several industrial sectors including automotive, aerospace, household appliances, marine, architecture, etc. The unique weight to strength ratio of aluminum makes it a perfect choice for applications in which light-weighting is a key concern. However, the soft nature of pure aluminum makes it prone to mechanical damage, and it is susceptible to corrosion in acidic and basic conditions. The drawbacks of pure aluminum can be resolved partially through its alloys but, depending on the elemental composition, different aluminum alloys possess unique benefits and shortcomings of their own. For example, copper rich aluminum alloys have excellent mechanical strength but suffer from inadequate corrosion resistance. Manganese rich alloys have outstanding corrosion resistance but poor machinability. Similarly, performance of magnesium and silicon rich alloys are very sensitive to the ratio of magnesium and silicon content. To solve these problems of aluminum and its alloys, anodization of aluminum substrates is a very popular technique practiced worldwide. However, anodization also has drawbacks; it is a costly process and also involves hazardous treatments.
This study presents the development of sol-gel based protective coatings that adhere directly onto untreated aluminum alloys and offer abrasion, corrosion and chemical resistance with a thickness of less than ten microns. The technology proposed here is an alternative to the chemically intensive and time consuming anodization process