Corrosion behaviour in salt spray and in 3.5% NaCl solution saturated with Mg(OH)2 of as-cast and solution heat-treated binary Mg–X alloys: X=Mn, Sn, Ca, Zn, Al, Zr, Si, Sr

Abstract

• Each Mg–X alloy corroded faster than high-purity Mg. • Alloys with high corrosion rates in immersion tests also had high salt spray corrosion rates. • There was a clear correlation with type of alloying rather than quantity of alloying. Corrosion of binary Mg–X alloys (as-cast and solution heat-treated) was characterised by immersion tests in 3.5% NaCl solution saturated with Mg(OH) 2 , and by salt spray. Alloys with high corrosion rates in immersion tests also had high corrosion rates in salt spray. Corrosion rates of the solution heat-treated alloys did not meet the expectation that they should be equal to or lower than those of high-purity Mg. There was circumstantial evidence that the higher corrosion rates were caused by the particles in the microstructure; the second phases had been dissolved. The corrosion rate of all alloys was faster than that of high-purity Mg.