Effect Of Inhibitors On Corrosion Behavior Of Magnesium Alloy In Sodium Chloride Solution

Magnesium alloys can be widely used because of their light weight,high stiffness/weight ratio,excellent die-casting and other advantages.Now,it has become an important engineering structure material.However,the high chemical reactivity and poor corrosion resistance of magnesium alloys severely restrict their applications.Among the many measures to suppress corrosion of magnesium alloys,addition of corrosion inhibitors is a kind of economic and effective method.So in this thesis,the inhibition behavior and inhibition mechanisms of the single component inhibitor and compound type inhibitors on AZ31 B magnesium alloy in 3.5 wt.% NaCl solution were studied by means of electrochemical measurements,weight loss measurements,scanning electron microscopy（SEM）and Fourier transform infrared spectroscopy（FT-IR）and other surface analysis techniques.The main research results are shown as follows.（1）When sodium diethyldithiocarbamate（SDDTC）,sodium acetate（NaAc）and disodium hydrogen phosphate（Na₂HPO₄）are used alone,the corrosion rate of AZ31 B magnesium alloy in NaCl solution can be effectively retarded.With the increase of corrosion inhibitor concentration,the inhibition efficiency increases first and then decreases.The best inhibition efficiency and the added concentration are obtained when they are used alone: when 5.0×10^-3mol L^-1 SDDTC is added,the inhibition efficiency is 69%;when 0.20 mol L^-1 NaAc is added,the inhibition efficiency is 80%;when 3.0×10^-3mol L^-1 Na₂HPO₄ is added,the inhibition efficiency is 92.9%.（2）When SDDTC and NaAc are used together,at a specific concentration,the two will have synergistic effects.The maximum inhibition efficiency is 90.4%,when the concentration is 10.0×10^-3mol L^-1 SDDTC + 0.15 mol L^-1 NaAc.Both SDDTC and NaAc conform to the Langmuir adsorption model,there appears a physical adsorption on the surface of magnesium alloy and forms a dense protective mixed film: SDDTC-Mg + NaAc-Mg + Mg（OH）₂.（3）Upon adding jointly SDDTC and Na₂HPO₄ into NaCl solution,the inhibition efficiency increases obviously.The maximum inhibition efficiency of 94% can be obtained,when the concentration is 2.0×10^-3mol L^-1 Na₂HPO₄ + 10.0×10^-3mol L^-1 SDDTC.The two kinds of inhibitors form a dense protective film on the surface of the magnesium alloy,which improves the corrosion inhibition efficiency and inhibits the corrosion of the magnesium alloy.