Corrosion behaviour of iron and AISI 304 stainless steel in tungstate aqueous solutions containing chloride

Abstract

O comportamento do ferro e do aço inoxidável AISI 304 frente à corrosão em solução aquosa de tungstato de sódio em presença de cloreto foi investigado usando as técnicas de voltametria cíclica, medidas de potencial de circuito aberto e impedância eletroquímica. Os resultados mostraram que a ação inibidora do ânion tungstato está relacionada com sua adsorção sobre a superfície eletrodódica e depende marcadamente da presença de oxigênio dissolvido no meio. Filmes formados por polarização anódica a baixas velocidades de varredura de potencial e rotação do eletrodo são mais estáveis permitindo um decréscimo na taxa de corrosão. Medidas de impedância eletroquímica em potencial de circuito aberto mostraram que a ação inibidora do tungstato é consideravelmente favorecida em tempos de imersão prolongados.The corrosion behavior of iron and AISI 304 stainless steel in aqueous tungstate solutions containing chloride ion was investigated by cyclic voltammetry, open circuit measurements and impedance spectroscopy. The obtained results point out that the inhibitive performance of tungstate depends on the presence of dissolved oxygen, being strongly related to the adsorption of this anion on the surface of the electrode. Under anodic polarization, at low sweep rate and electrode rotation the passive film is more stable and the corrosion rate decreases. At the open circuit potential, the EIS data have clearly demonstrated that for longer immersion times the tungstate inhibitive action is considerably improved.

Corrosion inhibition of AISI 1020 steel based on tungstate anion and amoxicillin as corrosion inhibitors in 0.05 mol l−1NaCl solution or inserted into cellulose acetate films

“…A phase angle increased from 66.5° to 75° indicating the beneficial effect of the tungstate anion on the AISI 1020 alloy. Similarly, the tungstate anion inhibitor effect was reported by Azambuja et al . on iron the same as for the 0.1‐mol l −1 NaCl concentration.…”

“…Then, a product layer begins to block the metal surface decreasing the anodic dissolution sites, even in the presence of chloride. The potential decline in longer immersion times, such as 3 or 7 days, is because of the competitive nature of the adsorption process between the aggressive and the inhibiting anions …”

“…The potential decline in longer immersion times, such as 3 or 7 days, is because of the competitive nature of the adsorption process between the aggressive and the inhibiting anions. [6] The electrochemical impedance measurements of the AISI 1020 steel alloy were carried out at the corrosion potential in 0.05 mol l À1 NaCl containing different concentrations of sodium tungstate: 0.0, 0.005, 0.01 and 0.07 mol l -1 according to Fig. 2.…”

“…There are a variety of methods for protection against the corrosion of ferrous alloys, based on the use of corrosion inhibitors or coatings …”

“…There are a variety of methods for protection against the corrosion of ferrous alloys, based on the use of corrosion inhibitors [1][2][3][4][5][6][7][8][9] or coatings. [10][11][12] The inhibitors used in the ferrous alloys are based on organic compounds such as mebendazole, [2] sulfonated compounds, [4,7] benzoate and acetate.…”