Optimising salt fog corrosion parameters to minimising the corrosion rate of AA7075-T651 alloy

Abstract

The most important property of aluminium is its ability to change its properties in a very versatile manner; it is amazing how much the properties can change from the pure aluminium metal to its most complicate alloys. There are more than a couple of hundreds of aluminium alloys and many are being modified from them. Aluminium alloys have very low density compared to steel; it has almost one thirds the density of steel. The aluminum-Zinc alloy system is very attractive to the aerospace industry due to its lower density, increased elastic modulus, increased fatigue crack growth resistance, easy formability and strength to weight ratio. As a consequence, this light alloy has shows potential future. However, these alloys have great affinity for chloride environment and other chemical oxidizing agents. The limitation of low corrosion resistance restricts their practical applications. The rolled AA7075-T651 plates were evaluated by conducting salt fog test in NaCl solution at different chloride ion concentrations, pH value and spraying time. Also an attempt was made to develop an empirical relationship to predict the corrosion rate of AA7075-T651 high strength Al alloy. Three factors five level of central composite design were used to minimize the number of experimental conditions. Response surface method was used to optimizing the corrosion rate of AA7075-T651 alloy. The developed relationship can be effectively used to optimizing t the corrosion rate of AA7075-T651at 95% confidence level.