Study On Properties And Mechanism Of Composite Corrosion Inhibitors For Copper In Sodium Chloride Solution

The inhibition behaviors of benzotriazole(BTA),sodium silicate and triethanolamine(TEA)on copper corrosion in 5%NaCl solution were investigated by means of static weight-loss test,scanning electron microscopy,polarization curves,electrochemical impedance spectroscopy.At different total concentration,the inhibition effect of five different proportions was compared between BTA and TEA,BTA and sodium silicate.The optimal combination of BTA,TEA and sodium silicate was studied by orthogonal test,and the effect of medium temperature,inhibitor concentration and immersion time on complex inhibitor was studied.The results are as follows:(1)The inhibition efficiency of BTA increases with concentration increasing in 5%NaCl solution.TEA has no inhibition effect to copper in 5%NaCl solution,and corrosion rate increases with the concentration of TEA increasing.The corrosion inhibition efficiency of sodium silicate on the corrosion behavior of copper in 5% NaCl solution refers to the concentration of sodium silicate,it promotes the corrosion of copper when the concentration is less than 50mg/L,and protects copper when the concentration is higher than 100mg/L.(2)Composite inhibitor(BTA and TEA)with a total concentration of 20mg/L,the best complex rate is 1:4,and the best complex rate is 4:1 when the total concentration is 50mg/L or 100mg/L.Composite inhibitor(BTA and sodium silicate)with a total concentration of 20mg/L,50mg/L or 100mg/L,the best complex rate is4:1.BTA and TEA,BTA and sodium silicate are produced inhibition synergies.(3)The optimal combination of complex inhibitor(BTA,sodium silicate and TEA)is BTA 50mg/L,sodium silicate 500mg/L and TEA300mg/L.The polarization curve data show that this compound inhibitor can inhibit the anodic reaction and cathodic reaction at the same time,and it belongs to Mixed-type inhibitor.AC impedance spectroscopy data showed the copper corrosion in in NaCl solution is influenced by charge transfer processes and diffusion process.The composite inhibitor hinders the process of charge transfer by forming a protective film on the copper surface,and the charge transfer resistance increases from 1161Ω to 27506Ω.(4)Considering the corrosion inhibitor usage and corrosion inhibition effect,composite corrosion inhibitor(BTA 20mg/L,sodium silicate 300mg/L and TEA 20mg/L)can meet the use requirement and save cost.The adsorption behavior of composite Inhibitor on copper surface conforms to Langmuir adsorption isotherm.The adsorption process is voluntary,the physical adsorption and chemistry adsorption exist at the same time.The inhibition efficiency of the complex inhibitor decreases with temperature increasing in the range of 28℃~65℃.With the increase of concentration of complex inhibitor,the corrosion rate of copper decreases and the inhibition efficiency increases.The polarization curve almost remain unchanged with soaking time 0.2h~3h at 35℃.The complex inhibitor is stable and protects copper effectively in NaCl solution.