In-situ Monitoring The Inhibition Effect Of Various Inhibitors On Metals By Electrochemical Noise Technique

Copper and Q235 steel are commonly used in industry.Because these metal materials are often exposed to corrosive liquid or acid,resulting in the service life of the metal materials greatly reduced and causing strong economic loss.As we all know,there are many anti-corrosion methods.Among them,inhibitors are widely used to protect metals from corrosion,which have advantages on economy and environment.Therefore it’s considerably significant to research inhibition effect of different kinds of inhibitors on two metals and mechanism.This paper systematically studied the relationship of concentrations of inhibitors as well as temperature in corrosive mediums and inhibition effect metals by using Electrochemical Impedance Spectroscopy(EIS),Electrochemical Noise(EN)techniques.The results show that:Studying the corrosion behavior of the inhibitor benzotriazole(BTAH)on the copper in 0.1 mol/L NaCl solutions,results showed that the inhibition efficiency(η)elevated with the increase of the BTAH concentration,up to 90.12%.With low concentration of BTAH inhibitor,the EN generated during initial film formation had large noise amplitude and little potential drift,with increasing the BTAH concentration,the EN features showed small noise amplitude and large positive potential-drift.New parameter Ec proposed from ENA,corresponding to the corrosion energy,was presented to further study the relationship between the EN feature and copper corrosion rate.The corrosion energy Ec decreases sharply when the BTAH concentration increases from 0 mg/L to 10 mg/L,and reduce little at the range of BTAH concentration from 10 mg/L to 40 mg/L.Another parameter of energy gap Eg obtained from CV results showed the opposite variation trend.Studying the corrosion behavior of the inhibitor ketoconazole(KCZ)on Q235 C-steel in 1 mol/L HCl solutions,the results showed that the inhibition efficiency(η)elevated with the increase of the KCZ concentration and the adsorption process followed the Langmuir isotherm with the value of Δ Gads0 being-41.82 KJ·mol-1,suggesting a stable and spontaneous inhibition process.It was also found that a new phase named Fe4NO2(OH)11 was formed during the adsorption process.In addition,the opposite variation of η and the pitting parameter Ej of Q235 C-steel with the increase of KCZ concentration indicates that EN technique can be used effectively to in-situ monitor the protection effect of an inhibitor.Studying the corrosion behavior of the inhibitor methylene blue(MB)on Q235 C-steel in 1 mol/L HCl solutions,the results showed that with the temperature increased,the inhibitor efficiency of low concentration(0-0.01 mM/L)of the inhibitor MB on Q235 C-steel in 1 mol/L HCl solutions decreased gradually;the inhibitor efficiency of high concentration 0.1-5 mM/L)of the inhibitor MB on Q235 C-steel in 1 mol/L HCl solutions has opposite trend.The inhibitor efficiency of the inhibitor MB on Q235 C-steel in 1 mol/L HCl solutions showed an increased tendency as the concentrations of the inhibitor MB raised.Hence,the inhibitor MB in low concentrations is mainly adsorbed on Q235 C-steel in the form of physical adsorption,that in high concentration is in the form of chemical adsorption on Q235 C-steel surface.