Electrochemical Properties Of Aluminum Alloy In Sodium Chloride Solution And Zinc Sulfate System

Aluminum has the advantages of light weight, good conductivity, and its surface can form a dense oxide film with a larger difference between the structure and the zinc crystal structure, so the pure aluminum plate cathode is widely used in the zinc electrowining as cathode. With the reduction of zinc concentrate grade and the increase of impurity content in electrolyte, the cathode corrosion cost increases. And the existing protection methods are difficult to achieve the ideal corrosion protection requirements.In this paper, commercial pure aluminum (99.6%), antirust aluminum (AA5083, Al-Mg), forging aluminum alloy (AA6061, Al-Mg-Si) and super hard aluminum alloy (AA7075, Al-Zn-Mg-Cu) are selected for research subjects. Fisrt, using potentiodynamic polarization curve, AC impedance spectrum and other traditional electrochemiacal methods, combined with in-situ electrochemical scanning microscope and immersion corrosion method, in-depth analysis the influence of alloy element to add on the corrosion resistance of aluminum alloy in 3.5% NaCl solution. Second, the characteristics of commercial pure aluminum, antirust aluminum, forging aluminum alloy and super hard aluminum alloy as the cathode were studied by systematic observations in the scanning electron microscope, X-ray energy dispersive spectrometry, sample test and electrochemical test.It had been found that alloy elements adding made the corrosion potential is more negative and the corrosion current density increases by traditional electrochemical method, scaning electrochemical and immersion corrosion method. But corrosion mechanism didn’t change, all of four samples are partial preferential corrosion, and then develop into a comprehensive corrosion. And the corrosion degree of different areas of surface c is different.Commercial pure aluminum, antirust aluminum, forging aluminum alloy and super hard aluminum alloy as zinc-electrowining cathode, found that alloying elements addition can increase the initial nucleation sites, promote the rate of nucleation; The nucleation rate increased to inhibit the corrosion of cathode by chloride ion. Under industry current density of 500 A·m-2, the deposition potential and overpotential of commercial pure aluminum, antirust aluminum, forging aluminum alloy and super hard aluminum alloy are Ecommercial pure aluminum=-1.541 V, ηcommercial pure aluminum=0.159V, Eantirust aluminum=-1.545 V, ηlantirust aluminum=0.161V,Eforging aluminum alloy 1.55 V, ηforging aluminum alloy =0.165V, Esuper hard aluminum alloy=-1.496V, ηsuper hard aluminum alloy=0.109V. Four material sample in zinc electrowinning industry condition of electrodeposited zinc tablets for five days, there is no change in crystal orientation. Forging aluminum alloy and super hard aluminum alloy is prone to buring plate and bubble, low current efficiency, were only 84.54% and 79.16%, the current efficiency of the pure aluminum was 88.04% and zinc deposition flat, smooth, but the cathode plate easy to corrosion by chloride ion. The quality of zinc deposition on antirust aluminum was similar with pure commercial aluminum’s. The current efficiency was 86.88%. But the inhibitory effect of corrosion on the chloride ion is obvious.