STUDY ON ATMOSPHERIC CORROSION RATE OF MG AZ31B IN BANDUNG AND BOSSCHA AND ITS CORROSION PRODUCT’S STABILITY TEST IN NACL, NA2SO4 AND ITS MIXTURE

• Main Author: Nur Azizah, Jasmita
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/67790
• Institution: Institut Teknologi Bandung

Atmospheric corrosion occurs when a thin layer of electrolyte forms on the metal surface. This layer is formed largely influenced by several parameters, including Relative Humidity (RH), Time of Wetness (TOW), type of location, rainfall, temperature, and atmospheric deposits such as [Cl-], [SO2], and [H+] which play a role important in atmospheric corrosion. These atmospheric conditions are very complex, so further studies are needed regarding their interactions with atmospheric metal corrosion. In this study, atmospheric corrosion testing was carried out to study the mechanism and characteristics of corrosion in magnesium alloy AZ31B in different environmental/atmospheric conditions. Bosscha Observatory area and Bandung City were chosen as the test locations because they have different environmental parameters. Atmospheric corrosion testing was carried out for 1, 2, and 4 months. Mass loss measurement results show that the longer the exposure time, the higher the atmospheric corrosion rate of the AZ31B alloy. In addition, the corrosion rate in the Mg AZ31B specimen in Bandung tends to be higher than the corrosion rate in Boscha. Furthermore, further characterization was carried out on the corrosion products formed on the surface of the specimen. Corrosion products on the surface of the specimen were observed through SEM observations, XRD, and FTIR tests. In addition, its corrosion resistance in NaCl and Na2SO4 solutions was studied by electrochemical methods such as OCP, EIS, and potentiodynamic polarization. SEM observations showed that the corrosion product formed on the surface of the specimen had a flower-like appearance, and there were many cracks. The results of the XRD and FTIR tests identified that the corrosion products formed on the surface of the specimen were MgO and Mg(OH)2. OCP testing showed that the corrosion products in all specimens had a negative initial OCP potential, which tends to increase over time. OCP testing showed that the corrosion products in all specimens had a negative initial OCP potential, which tends to increase over time. OCP result testing shows that the formed passive layer becomes more protective over time. The results of the Tafel polarization test showed that the corrosion products formed experienced the most significant increase in the corrosion rate in the Na2SO4 solution compared to the NaCl solution and the mixed solution. The EIS test showed that the corrosion product layer formed had a double semicircular Nyquist curve, indicating the occurrence of uniform and local corrosion phenomena.