The Investigation On Corrosion Inhibition Effect And Mechanism Of Polyaspartic Acid To Copper In HCl Solution

The corrosion and protection of copper has been an important studied topic in corrosion sciences for many years. Polyaspartic acid (PASP), a kind of Environmentally Benign, nontoxic and biodegradable corrosion inhibitor, has become the study focus in chemistry, water treatment and medicine in the past decade. But it is rarely find some technical reports about PASP as an inhibitor of cooper in HC1 solution. In this paper, the corrosion inhibition ability and mechanism of PASP with copper in 0.5mol/LHC1 solution are discussed with the methods of electrochemical impedance spectroscopy, potentiostatic polarization and cyclic voltammentry. The primary results are as following: 1 .Potentiodynamic polarization curves show that:(1)PASP can inhibit the reaction of cathode and anode when copper is added into 0.5 mol / L HC1 solution, but the cathode inhibition is primary.(2)The corrosion inhibition efficiency increases when PASP concentration is going up. And when the concentration is reached 2 g/L, the corrosion inhibition efficiency will be stable. The corrosion inhibition efficiency is 90.89% under the concentration is 20 g/L at 20 °C. 2.Cyclic voltammetry indicate that:PASP could restrain the reaction of cathode and anode simultaneously. It could cause the cathode and anode summit currents decrease. That is less copper anion in the environment. PASP has the effect of corrosion inhibition in hydrochloric acid solution. In addition the potation of cathode summit current turned negative as increasing PASP concentration, and the potential of anode summit current turned positive, it can constrain the corrosion of copper. That is to say PASP is a mixed corrosion inhibitor and can constrain the corrosion of copper surface. 3.1mpadance measurements show that:(1)PASP have effect of inhibition under different concentrations, the inhibition efficiency of PASP increases with the rise of PASP concentration at 20°C.The maximum inhibitorefficiency was 81.45% when the concentration is 50 g/L.?The inhibitor ability of PASP decreases with temperature increasing in the experimental temperature.4. It is linear relationship between the corrosion inhibition coefficient and PASP concentration. The adsorptive behavior of PASP for copper follows the Freundlich adsorption isotherm logr) = logK + nlogC in 0.5mol/L HC1 solution under experimental temperature. At 20 °C, the formula of isotherm is logr| = 2.21 + 0.111 logC, the free energy of adsorption value is -22.18 KJ/mol <0, which indicate the adsorption of PASP on copper surface is spontaneous5. PASP and the typical cationic surfactant -cetyltrimenthyl ammonium bromide (CTAB) have better positive function and restrain the cathode. When the concentrations ratio is 4:1, the PASP concentration is 0.016 g/L and the CTAB concentration is 0.004 g/L, it is better than each of these two chemicals is used separately. The best inhibition efficiency is 89.30%,it is more than 67.70% that PASP is used alone.