Study On Inhibition Effect Of Sodium Silicate For6063Aluminium Alloy In3.5%Nacl Solution

Aluminium and its alloys are widely used in marine environment because of theirlow density, high specific strength and good corrosion resistance. However, theoxidation film of aluminium alloy can be damaged by a large number of chloride ions inseawater. Therefore, the corrosion resistance of alloys will be decreased. Corrosioninhibition has become an important method of suppressing metal corrosion. It is causedby its simple operation, economical applicability, prominent effection and no additionalequipment, etc. There are many reports about inhibitors of aluminium and its alloys, butmost of these inhibitors are toxicity, expensive and making environmental pollution.Therefore, research on environmental-friendly inhibitors to protect the environment andruduce resources consumption is necessary.The inhibition behavior of sodium silicate inhibitor effects on corrosion of6063aluminium alloy in3.5%NaCl solution have been studied using polarization curve,electrochemical impedance spectroscopy（EIS） and surface morphology analysismethods. As sodium silicate is a kind of economical green corrosion inhibitor with theadvantages of rich resources, environmental protection and low-cost, et al, putting itinto the use of the aluminium alloy corrosion inhibition has great significance. Theinhibition performance and mechanism of the inhibitors were carried out. Theconclusions as follows:EIS results indicat that sodium silicate inhibit the corrosion of6063aluminiumalloy effectively in3.5%NaCl solution. The inhibition efficiency increases with anincrease in sodium silicate concentration and time of immersion, the best inhibitionefficiency reaches when the concentration of inhibitor is0.8mmol·L^-1. Moreover, asthe concentration increasing continuously, inhibition efficiency is decreased down alittle. Polarization curves show that sodium silicate is a mixed type inhibitor, which iscaused by blocking the rate of both the anodic and cathodic reactions in corrosionprocess.In order to study the adsorption behavior of sodium silicate on6063aluminiumalloy, the data of inhibition efficiency of the polarization test were substituted intomodel of Temkin, Frumkin and Langmuir, respectively. And results showed that theabsorbed behaviour was fitted with the Langmuir adsorption isotherm model. That thecorrosion inhibitor adsorbed on6063aluminium alloy surface was accorded with Langmuir adsorption isotherm. The values of G adsduring the adsorbed process arenegative. Thermodynamic parameters revealed that adsorption process is spontaneous.Physisorption was proposed as the mechanism for the corrosion inhibition.Kinetic results showed that the apparent activation energy Eavalues for6063aluminium alloy corrosion in inhibited solutions are higher than that for the uninhibitedsolutions. Because the corrosion inhibitor molecules adsorbed on the surface of6063aluminium alloy and covered those superficial corrosion activity centers, so theactivation energy increased, and naturally the corrosion of6063aluminium alloy in3.5%NaCl solution was inhibited.