The corrosion behaviour of a dissimilar metal friction stir weld between AA2024-T351 and AA7010-T7651 was investigated. Gel visualisation and immersion tests were used to examine the effect of galvanic coupling between the two components. A microelectrochemical cell with a 400 mm diameter glass tip was used to measure the anodic and cathodic reactivities at different positions in the weld region as well as in the base alloys. It was found that the net anodic attack was in the 7010 alloy with the highest susceptibility in the nugget region. The nugget region of 2024 was protected by its high net cathodic reactivity owing to the precipitation of S phase particles.
Cryogenic cooling with CO 2 was applied during friction stir welding of AA2024-T351 in order to reduce the temperature increase during welding, and thus improve the corrosion resistance of the weld. The effect of cryogenic cooling on corrosion susceptibility was investigated with gel visualisation, immersion tests and local electrochemical measurements. The most susceptible area for both uncooled and cooled welds was in the heat-affected zone (HAZ) region, which showed intergranular attack. Cryogenic cooling had no detectable influence on the degree of anodic reactivity in the weld region. However, it did decrease the width of the reactive HAZ.
Purpose -The purpose of this paper is to understand the effect of pressurized steam on surface changes, structures of intermetallic particles and corrosion behavior of AA1050 aluminium. Design/methodology/approach -Industrially pure aluminium (AA1050, 99.5 per cent) surfaces were exposed to pressurized steam produced from a commercial pressure cooker at the maximum temperature of 116oC for 10 min. Surface morphology was observed using SEM-EDX and FIB-SEM. Phase identification and compositional depth profiling were investigated using XRD and GDOES, respectively. Potentiodynamic polarization measurements were used to study corrosion behavior. Findings -A 590 nm boehmite oxide layer was generated on AA1050 associated with partially dissolved and/or fallen off Fe-containing intermetallic particles after exposure to pressurized steam. A significant reduction (25 times) in anodic and cathodic reactivities was observed due to the formation of the compact oxide layer. Originality/value -This paper reveals a detailed investigation of how pressurized steam can affect the corrosion behaviour of AA1050 aluminium and the structure of Fe-containing intermetallic particles.
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