Corrosion of 1050 aluminium in coastal atmospheres

Abstract

Very few studies on the atmospheric corro-sion of aluminium in coastal areas have considered a wide range of atmospheric salinities. This paper reports the results of research carried out at six testing stations located in pure marine atmospheres at different distances from the shoreline at Cabo Vilano wind farm (Galicia). 1050 aluminium test specimens were exposed in the marine atmospheres for 3, 6, 9 and 12 months, determining the corrosion experienced by aluminium (pitting formation) as a function of exposure time. The nature and composition of the corrosion products formed was analysed by grazing incidence X-ray diffraction and the morphology of the attack experienced by the aluminium was studied by scanning electron microscopy with energy dispersive X-ray spectrometry. The most salient results include the following: (a) The corrosion rate decreases with distance from the shoreline and with exposure time, (b) The corrosion product formed is gibbsite, (c) The development of pitting is due to the presence of Cl- and SO42- anions from the marine aerosol that migrate to the bottom of the pits.