THE EFFECT OF CRYOGENIC TREATMENTS ON PITTING CORROSION SUSCEPTIBILITY OF AA5083-H111 IN 3.5% NaCl ENVIRONMENT

Application of aluminium alloys is increasing in all industries due to its combined properties of low weight, good mechanical resistance, thermal conductivity, electrical conductivity, high strength, and good corrosion resistance. In particular, AA5083-H111 alloys have been successfully used in the maritime sector. Unlike purely surface treatments, cryogenic treatment is an inexpensive one-time process that influences the core properties of the components. Cryogenic treatment has recently been introduced to Al alloys. Although the main mechanisms are still ambiguous, considerable improvements on mechanical properties are well noted. However, the effect of cryogenic treatment on the corrosion of Al alloys is limited. This study investigated the effect of shallow cryogenic treatment (-80 °C) on the corrosion of 5083- H111 aluminium alloy, which is used particularly in the shipbuilding industry. Plates of 6-mm thickness exposed to a 3.5% NaCl environment were evaluated via Brinell hardness measurements, Electrochemical Impedance Spectroscopy (EIS) and surface monitoring methods including atomic force microscopy (AFM) and optical profilometry (OP) applied before and after the effect of cryogenic treatment. Results indicated that the duration time of cryogenic treatment (24 h, 36 h and 48 h) had little effect on changing the hardness values and corrosion response of AA5083-H111 alloy in the 3.5% NaCl environment.