Alcoholate corrosion of aluminium in ethanol blends -the effects of water content, surface treatments, temperature, time and pressure

Sammanfattning: As it becomes more important to replace fossil fuels with alternative fuels, biofuels like ethanol are becoming more commercially used. The increased use of ethanol brings good influences such as lower impact on the environment. However, the use of ethanol can also bring negative effects regarding corrosion of metals. In the automotive industry aluminium has been seen affected by a novel very aggressive corrosion phenomenon, alcoholate corrosion. This master thesis investigation has investigated the effect of a few parameters of importance for alcoholate corrosion; water, temperature, time and pressure. The aluminium alloys AA6063 and A380 have been investigated and the capacity of five different surface treatments of AA6063 has been tested to observe if they inhibit the effect of alcoholate corrosion.   Throughout the experiments the water dependence of alcoholate corrosion has showed to be of large importance for the corrosion process. An increase in water content will postpone the start of alcoholate corrosion or prevent corrosion to occur.  A correlation between temperature and time has been observed. Higher temperatures results in a shorter time period of exposure before alcoholate corrosion occurs, and vice versa. The effect of different pressures was investigated and showed no effect on alcoholate corrosion when using pressurisation with the inert nitrogen gas.   All surface treatments revealed a capacity to protect the aluminium alloy against alcoholate corrosion to different extent. The electroless nickel plating seemed to prevent alcoholate corrosion while the Keronite coating seemed more sensitive to this form of corrosion.