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The Study on Corrosion Behavior of AZ91D Magnesium Alloy by Indoor Simulated Test

Author: LiangJianNeng
Tutor: LinCui
School: Nanchang University of Aeronautics and
Course: Materials Physics and Chemistry
Keywords: Indoor simulation experiment AZ91D magnesium alloy Thin liquid film Corrosion Behavior
CLC: TG172.3
Type: Master's thesis
Year: 2010
Downloads: 91
Quote: 1
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Abstract

This article using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) and other means of Modern Physics AZ91D magnesium alloy in the pollution-free atmosphere environment, SO2 atmospheric environment as well as analog acid rain environment in the corrosion behavior, and the atmospheric corrosion thin liquid film electrochemical measuring device to explore the electrochemical behavior of magnesium alloy thin liquid film, and finally to establish on the basis of the experimental magnesium alloy in the atmospheric environment, and SO2 pollution-free atmosphere environment The kinetic model. Environment pollution-free atmosphere of 95% relative humidity, the magnesium alloy at 20 ° C, 30 ° C and 40 ℃ corrosion growth re-meet the exponential increase in law. The elevated temperature can accelerate corrosion of the magnesium alloy. Corrosion products focused on the surface of the α-phase, and mainly in the growth of cellular morphology, cellular product by a large number of needle-like product. The corrosion products are mainly of MgO and Mg (OH) 2, the temperature rises, the content of the Mg (OH) 2 increases. SO2 atmosphere, with the increase in SO2 content of magnesium alloy corrosion intensified. Volume fraction of 0.4 × 10-6,1 × 10-6 and 2 × 10-6 SO2 atmosphere, corrosion weight gain increased exponentially law; volume fraction of 4 × 10-6SO2 atmospheric environment, corrosion weight gain by the linear increase and the index increased two phases. Corrosion products to granular growth, forming a continuous product layer over corrosion process, the crack occurs at a product of the large particles in the corrosion product layer. The corrosion products are mainly for MgO, Mg (OH) 2, MgSO3 · 6H2O, MgSO4 · 6H2O. The corrosion time extension, and SO2 content increase, MgSO3 · 6H2O, MgSO4 · 6H2O increase. Simulated acid rain environment, the corrosion area can be divided into weak corrosion area and strong corrosion zone; magnesium alloy surface corrosion pits formed in the initial stage of corrosion, mainly generated by the dissolution of the magnesium alloy matrix. Magnesium alloy surface in a simulated acid rain will be a lot of pitting corrosion morphology, while the needle-like corrosion products covering the surface of the specimen, the last needles clogging the pits the formation of the occluded cell. Simulated acid rain and SO2 in the atmosphere, there are obvious differences in morphology and corrosion mechanism of magnesium alloy corrosion, which is mainly due to simulated acid rain solution containing aggressive anions, and more acidic, while the SO2 atmosphere magnesium alloy cathode The reaction of oxygen reaction, and simulated acid rain by hydrogen evolution reaction. With the thinning of thin liquid film in a non-polluting, and SO2 atmosphere, the corrosion potential of magnesium alloy first negative and then positive shift of the corrosion current density first increases and then decreases, limiting diffusion current density first increases and then decreases. SO2 atmosphere Nyquist plots under the thin liquid film diffusion impedance by a high-frequency capacitive loop and a low-frequency performance, the two time constants. AC impedance test that, 1/Rct increasing with the conduct of corrosion, corrosion tendency of different thickness containing SO2 THIN FILM order: 50 μm gt; 20 μm gt; 200μm gt; ontology. With the data obtained by the laboratory simulation experiments, the kinetic model is divided into gas dissolving, gas in the thin liquid film in the hydrolysis and the formation of corrosion products, through the integral calculus to the generation amount of the different periods of corrosion products accumulate, the magnesium alloy in the final calculated non-polluting, and SO2 in the atmospheric environment corrosion weight gain, and compared with experimental data to verify the validity of the model.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metal corrosion protection,metal surface treatment > Various types of metal corrosion > Atmospheric corrosion, corrosion of gas
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