Study On Synergistic Inhibition Effect Of SDBS And Isoniazid For Brass In3.0%NaCl Solution

Corrosion inhibition has become an important method of suppressing metalcorrosion for its simple operation, economical applicability, prominent effection, lessside effects, and no additional equipment, etc. Copper and its alloy have the property ofcorrosion resistance, but still can be severely corroded in corrosive system. There aremany reports about copper inhibition, mostly for benzotriazole compounds, but whichare lack of economical applicability and will cause environmental pollution. In order toresponse the environmental protection and resources economized, studying thefriendly-environmental corrosion inhibitors is very application and theoretical.This paper mainly applyed weight-loss experiment, electrochemical test, surfacemorphology analysis and quantum chemical calculation to study isoniazid and SDBSused as alone or combination as the corrosion inhibitors of brass in3.0%NaCl solution,which are easy to be decompound. Isoniazid is an organic compound containingheterocyclic nitrogen and strong negative polar groups of nitrogen, oxygen, no report onthese compounds as corrosion inhibitors for metals has been published. SDBScontaining polar groups of sulfonic acid root, can adsorb on to the copper surface, inaddition, the long alkyl chain can form a hydrophobe layer between copper and solution,to guarantee the adsorption groups be stable. This paper studied the inhibitionperformance and inhibition mechanism of the two inhibitors, obtaining someconclusions as follows:When isoniazid used alone, corrosion inhibition efficiency increases with theconcentration increasing, the best inhibition efficiency reaches when the concentrationis0.50g/L, and decreasing with the concentration continuous increasing. When SDBSused alone, corrosion inhibition efficiency increases firstly and decreases afterwardwith the concentration increasing, the best inhibition efficiency reaches when theconcentration is1.74g/L. Both of the corrosion inhibitors adsorb on to brass surfacefollowing Langmuir adsorption isotherm, gibbs free energy△Gθads<0, shown that theadsorption process is spontaneous, and the adsorption of the two inhibitiors is the resultof joint action of physical adsorption and chemical adsorption, preferring physicaladsorption.The inhibition efficiency markedly enhanced when isoniazid and SDBS used ascombination, corrosion potential shifts toward positive direction obviously, exibiting an anodic corrosion inhibitor. The inhibition efficiency reached above95%when theconcentration of isoniazid and SDBS is0.50g/L and0.35g/L, respectively. The resultsindicated that the synergistic effect of isoniazid and SDBS can effectively suppress thebrass corrosion reactions, because when isoniazid is enough, it can fill the gap betweenthe SDBS molecules, forming a denser protective film.Investigation how the system pH can effect the inhibition efficiency of the bestalone and best mixture of isoniazid and SDBS. The results prove that the inhibitionefficiency of isoniazid and SDBS in alkaline is better than that of in acid or neutralsolution. Because in alkaline conditions, brass surface can form Cu2O protective film,otherwise, isoniazid is less susceptible to be proton, and SDBS will also keep theactivity of the polar groups of sulfonic acid root, so the Cu2O film and the adsorptionfilm can protect brass together.Rising the system temperature, would make the corrosion products film andinhibitor adsorption film breaken off, speeding up the corrosion reaction of brass.Because isoniazid and SDBS preferring to physical adsorption, rising temperature willaffect the stability of the adsorption film. And the relationship of corrosion rate is thatno inhibitor single inhibitor combination inhibitor.According to quantum chemistry calculation, we know the activity adsorptioncenters of isoniazid and SDBS, having researched some information about the chargeand structure of the inhibitor molecules, and giving some corrosion inhibitionmechanism of the single and combination inhibitors in theoretically.The results of pyrogenation shown that isoniazid is easy to be decompounded, thedegradation temperature and the apparent activation energy are lower than the otherrelative contaminant.