The Study Of Corrosion Inhibitors Of Nonferrous Metals In Nitrate Acid

The inhibition effects of lots of compounds were studied by the weight loss method, andthe results indicated that SDS and thiourea were better inhibitor for zinc and aluminum，respectively. So SDS and thiourea were selected as research objects for exhaustive study. Theinhibition effects of them for nonferrous metals in nitrate acid were studied by adsorptiontheory and electrochemical polarization curve method.The results showed that the single molecule layer of these compounds adsorbed on thesurface of the nonferrous metals and the regularity of absorption followed Langmuirisothermal equation. The adsorption process of the two compounds was spontaneous,exothermic and entropy reducing. The adsorption ability and corrosion inhibition efficiencydecreased with the temperature rising. Electrochemical polarization curves indicated that SDSwas an anodic type inhibitor, while thiourea was a cathode type inhibitor. The corrosioncurrent density was decreased obviously in the presence of inhibitors.The inhibition efficiency was improved significantly by synergistic effect. Thecomposite corrosion inhibitors with excellent corrosion inhibition efficiency for zinc andaluminum in nitrate acid were composed by orthogonal method. Corrosion inhibition effectsof the two composite corrosion inhibitors had been evaluated. The effects of theconcentration of composite corrosion inhibitors, the nitrate acid concentration, thetemperature and time on the corrosion rate of the two nonferrous metals had been studied. Theresults showed that this composite corrosion inhibitor behaved excellent corrosion inhibitioneffects in different temperature, acidity and time. The corrosion velocity of nonferrous metalsaccorded with national standard (<6g m-2h-1). Electrochemical polarization curves indicatedthat the composite corrosion inhibitor for zinc was a mixed type inhibitor and the compositecorrosion inhibitor for aluminum was an anodic type inhibitor. The photos of nonferrousmetals surface had been taken under the different corrosion condition. The photos showed thatpartial corrosion was not observed on nonferrous metals surface. So the mechanicalperformance of nonferrous metals had not been changed in the presence of these compositecorrosion inhibitors. These composite corrosion inhibitors were excellent corrosion inhibitorsfor nonferrous metals in nitrate acid.