Study Of Inhibitors For AZ91D Magnesium Alloy In NaCl Solution

Magnesium alloys are widely used in the area of aerospace industry,automobile and electronic industry.Due to its bad corrosion resistance,magnesium alloys haven't been widely used as aluminium alloy. In a harsh environment with Cl-,magnesium alloys have very poor corrosion resistance.The corrosion of magnesium will not happen in the alkaline solution with pH>11.5.It is important to solve the problem of the corrosion of magnesium,so that we can promote the comprehensive application and the industrial development of magnesium alloys in our coumtry.By using electrochemical polarization curves,full-immersion weight-loss expriment to do the selecting work and analyse their effects to the electrochemical procedure of magnesium alloy,this article gets four inhibitors with excellent inhibition efficiency for AZ91D magnesium:0.7% diaminomethanal-77.17%,0.5% thiourea-78.36%,0.1% SDEDTC-58.65%, 0.5% imidazoline-70.90%.According to the inhibition efficiency study of the organic-organic and organic-inorganic compounds with the already selected inhibitors, we get the best inhibition efficiency of every compounds with ratios as following:with 0.3% thiourea+0.1% SDEDTC and 0.5% thiourea+0.5% SDEDTC-which both are 88.17%ï¼›with 0.3% thiourea+0.1% imidazoline-91.61%ï¼›with 0.5% Na3P04+0.5% SDEDTC-90.80%ï¼›with 0.1% Na3PO4+0.5% thiourea-88.10%ï¼›with 0.3% Na3PO4+0.1% imidazoline-90.10%.Based on the inhibition efficiency study of inhibitor compounds,we can find that thiourea+SDEDTC and Na3PO4+SDEDTC show a very good synergistic effect.The compounds have improved the protecting effect for magnesium alloy,showing a higher inhibition efficiecy than any of the used compound inhibitors.Though the inhibitor compounds of thiourea+imidazoline,Na3PO4+ thiourea and Na3PO4+imidazoline also showed a better inhibition efficiency with certain ratios,the ihhibition efficiency varies with changes of concertration and ratio.They don't have synergistic effect with each other. According to the electrochemical tests and XPS analysis,it is believed that between the inhibitors exists competitive adsorption,which leads to the result that the ihhibition efficiency varies when concertration and ratio of inhibitor changes.