Sapa has developed an enhanced anodising process that offers a much-improved resistance to corrosive chemicals on the market. It is needed in an increasingly tough world for cars. Even at the car wash, more aggressive cleaning fluids are taking the shine off aluminium components faster than ever before.
Test samples
Anodising is a widely used surface treatment for aluminium alloys that provides a protective coating by oxidising the metal by electrolysis in sulphuric acid. The benefits are increased resistance to corrosion and wear, and anodising provides better adhesion for paint primers and adhesives than bare metal.
“The new anodising process consists of a new type of corrosive-resistant coating that has the ability to inhibit the attack of alkalis on the surface of the anodised aluminium,” says Richard Shaw, Anodising Manager at Sapa Components Ltd in the UK.
The process has been developed in response to the automotive industry’s need for more corrosion-resistant car components, particularly as increasingly aggressive alkali chemicals are used more and more in high-pressure car cleaning. Strong alkalis degrade anodised aluminium coatings quickly, and the growing use of aluminium by vehicle manufacturers has prompted intense development activity to address this issue.
To give some idea of the improvement, Shaw says: “Standard aluminium oxide films are usually stable between a pH range of 4 to 8. The coating that we intend to offer is in excess of 12.5 pH.” As the pH scale is logarithmic with a maximum value of 14 for the strongest alkalis, the actual increase from 9 to 12.5 represents a vast improvement over existing levels. “Details of the process are a closely guarded secret”, says Tony Wall, Sales Director at Sapa Components Ltd.
“We had to overcome considerable technical hurdles,” he says “to achieve a coating with the right physical characteristics to deal with increasingly corrosive alkali exposure. The two-year development programme along with our main chemical partners has added an extra dimension to the anodising capabilities at Sapa. “The make-up of the new chemical formula is key to the process,” Wall says.
As well as benefiting existing exterior aluminium car components, the new coating offers vehicle manufacturers the ability to use this lightweight and recyclable material more widely. Cutting the overall weight of a vehicle saves fuel consumption and reduces carbon dioxide emissions. In addition, the resistant aluminium coating also offers the attractive finish that is used increasingly in exterior trim components.
The new coating has been tested on a number of automotive components such as roof rails, window surrounds and grilles with major car companies including General Motors, Ford, Jaguar and Aston Martin. And following the success of these trials, the company had its first volume product order with a major original-equipment manufacturer for finishing of a new exterior trim, Wall says.
For further information please contact Tony Wall, Sales Director Sapa Components Ltd +44 770 27 11 385 or Gabriella Ekelund, Communications Director Sapa AB +46 70 953 08 53.