Effect of additional Si and Cu on strength and corrosion resistance of sacrificial anode fin stock for automotive heat exchangers

To investigate the effects of Si and Cu on strength and corrosion rate of sacrificial anode fin stock of Al–1.5%Mn–0.2%Fe–1.5%Zn alloy for automotive heat exchangers, tensile test and SWAAT have been carried out. Strength increased with Si and Cu addition. Corrosion rate did not increase with Si addition in spite of increase of α-AlMnSi compound density, because the compounds did not work as effective cathode in the alloy. On the other hand, corrosion rate increased with Cu addition. This was explained in the existence of deposited Cu on the specimen surface during SWAAT worked as strong cathode in the alloy. Cathodic polarization characteristics in 3.5% NaCl solution rather than in SWAAT solution were effective to evaluate corrosion rate of the alloys in SWAAT.