Crevice-Galvanic Corrosion in Aluminium Shower Curtain Poles

Abstract

Light microscopy, scanning electron microscopy and energy dispersive X-ray analysis were employed to identify the key factors responsible for the crevice-galvanic corrosion of shower curtain poles produced from EN AW-6060 alloy. The corrosion process has started between the aluminium poles and the metallized plastic hooks used to hang the shower curtains on the poles. The highly alkaline bathroom cleaning agent has penetrated between the aluminium profile and the plastic hooks leading to the dissolution of the unusually thin anodic oxide layer. The aluminium profile which has been stripped of its anodic oxide locally via crevice corrosion is then allowed to contact the Ni-, Cr- and Cubearing coating of the plastic hooks. The corrosion process has accelerated due to a galvanic couple effect as evidenced by the analysis of the corroded regions where Cu and Ni were abundant.

Analysis of macro segregation in twin-roll cast aluminium strips via solidification curves

“…The latter is inherited from dendritic solidification and scales with dendrite arm spacing which is in the order of several microns. Micro segregation is not a serious threat to the quality of the sheet products processed from TRC aluminium strips and is thus tolerated unless customer applications involve demanding forming operations [2]. Besides, high temperature annealing treatments employed at the start of down stream processing help to homogenize dendritic segregation.…”

“…In spite of improved homogeneity achieved by high solidification rates, twin-roll cast (TRC) aluminium strips reveal macro as well as micro segregation [1][2][3]. The latter is inherited from dendritic solidification and scales with dendrite arm spacing which is in the order of several microns.…”

“…Macro segregation in TRC aluminium strips, on the other hand, is most pronounced near the centre plane of the strip and cannot be taken care of with a homogenization cycle [4]. This type of segregation could range from a mild and gradual coarsening of the Al-Fe based intermetallic particles to solute-rich channels running more or less parallel to the casting direction [1][2][3]. The latter is referred to as the centreline segregation and is analogous to the channel segregation often encountered in ingots and slabs [2].…”

“…This type of segregation could range from a mild and gradual coarsening of the Al-Fe based intermetallic particles to solute-rich channels running more or less parallel to the casting direction [1][2][3]. The latter is referred to as the centreline segregation and is analogous to the channel segregation often encountered in ingots and slabs [2]. The severity of centreline segregation is claimed to be linked with the solidification behaviour which in turn is dictated by the alloy composition [1].…”