| Copper alloy can be widely used because of many advantages including good mechanical, formability, corrosion resistance, and so on. It has become an important industrial material, instead of carbon steel used in more and more field such as heat exchange pipe or cooling systems piping. But in seawater, severe corrosion can be occured for copper alloy. Every year copper alloy corrosion brings great harm. Use of inhibitors for the corrosion of copper alloy is very cost effective way. However, with the development of industry and people's environmental awareness, some toxic and harmful inhibitors will be restricted or banned. Therefore, the research of efficient and environmentally friendly corrosion inhibitors for brass H62 in 3.5% NaCl solution is used very significantly for promoting the application of copper alloy and giving full play to its performance advantages.According to the direction of research and development of environmental protection and efficient, By means of electrochemical methods, the concentrations of single component sodium gluconate, sodium acetate, SDBS, ZnSO4 on the inhibition effect for brass H62 were studied in 3.5%NaCl solution at 30℃. Below its optimal concentration, the synergistic inhibition effect of sodium gluconate-based separately with sodium acetate and sodium dodecylbenzenesulphonate was studied. With sodium gluconate, sodium acetate and sodium dodecylbenzenesulphonate as the main inhibiting component, the corrosion inhibition performance of three composite inhibitor was explored. In this basis, zinc sulfate was added to form an environmentally friendly four composite inhibitor choosing sodium gluconate as main agent. The four factors affecting the four composite inhibitor were studied, for example, temperature, time and dynamic media. At last the mechanism of the inhibition was speculated.The results of experiments showed that: in 3.5% sodium chloride solution, the single use of sodium acetate, SDBS, ZnSO4 had some corrosion inhibition effect for brass H62. The best concentrations of single component corrosion inhibitor were 100mg·L-1, 70mg·L-1, 70mg·L-1 and 130mg·L-1 respectively.The complex of sodium gluconate had a synergistic effect with sodium acetate and SDBS. The best ratio of sodium gluconate and sodium acetate is 60:10. The complex of three inhibitors on brass H62 had good corrosion inhibition effect. When the concentration ratio was 60:10:30, the inhibitive efficiency could be achieved 84.61%. With the addition of different concentrations of zinc sulfate, the inhibitive efficiency of the inhibitor was further improved. The optimum formulation was sodium gluconate of 60mg·L-1, sodium acetate of 10mg·L-1, SDBS of 30mg·L-1 and ZnSO4 of 30mg·L-1.When the critical concentration is 200mg·L-1, the inhibitive efficiency is 97.96%. The four composite inhibitor showed good corrosion inhibition for brass H62 at the temperature from 20℃to 50℃, the time from 1h to 5h, in low and middle speed conditions. Inhibitive efficiency increased with the concentration.Finally, the corrosion inhibition mechanism of composite inhibitor was studied by electrochemical polarization curve and optical microscopy. The results showed four composite corrosion inhibitor formed a layer dense, uniform and stable corrosion inhibition film on the electrode surface. The protective film prevented the corrosion medium adsorption and corrosion of brass H62. The inhibitor was a mixed type inhibitor which mainly inhibited cathode process.
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