Effect of temperature change rate on the critical pitting temperature for duplex stainless steel

Abstract

The effect of temperature change rate on the critical pitting temperature (CPT) for two kinds of duplex stainless steels (DSS, namely UNS S31803 and UNS S32750) in 1 mol L -1 NaCl solution was investigated using the potentiostatic current transient technique. The values of CPT for two DSSs all increased as the temperature change rate (t) increased. A linear relationship between the CPT and the square root of temperature change rate (t 1/2 ) was found. Furthermore, deriving from the point defect model (PDM), this particular relationship received theoretical support at low temperature change rates. KeywordsDuplex stainless steel Á Pitting corrosion Á Critical pitting temperature Á Temperature change rate Á The point defect model List of symbols J ca Cation diffusion rate at the metal/film interface/ cm -2 s -1 J m Rate of elimination of cation vacancies at the metal/film interface/cm -2 s -1 t Incubation time for passivity breakdown at a single site/s J 0 Parameter defined by Eq. 3 u Parameter defined by Eq. 4 F Faraday's constant (96,487°C mol -1 ) V extApplied potential with respect to a reference electrode/V R Gas constant (8.314 J K -1 mol -1 ) TAbsolute temperature/K a Cl À Activity of chloride ion/mol L -1 K Parameter defined by Eq. 6 D ÃAvogadro's number (6.023 9 10 23 mol -1 ) DG 0 S Change in Gibbs energy for Schottky-pair reaction/J mol -1 DG 0 AÀ1 Standard Gibbs energy change for absorption of an aggressive species into an oxygen vacancy at the film/solution interface/J mol -1 / 0 f=s Constant/V D 0 Diffusion coefficient/cm 2 s -1 DE Diffusion activation energy/J mol -1 T cpt Critical pitting temperature for passivity breakdown at a single site/K DT Over temperature for passivity breakdown at a single site/KGreek letters s Time for passivity breakdown at a single site once a critical vacancy condensation had been achieved/s n Critical concentration of cation vacancies for passivity breakdown/cm -2 v Stoichiometry of the passive film, MO v=2 ; and the oxidation state of the cation a Dependence of potential drop across the film/solution interface on the applied potential X Mole volume of the barrier layer per gram-atom of the cation/cm 3 mol -1 b Dependence of potential drop across the film/solution interface on pH e Field strength in the passivity film/V cm -1 n 0 Defined by Eq. 12 t Temperature change rate/K s -1

A double‐mode cell to measure pitting and crevice corrosion

“…By this method, the average CPTs of the 2205, S32760, and 2507 stainless steels were measured to be 59.55, 75.70, and 79.68°C, respectively. They were close to the values reported in literatures …”

Localized Corrosion: Passive Film Breakdown vs Pit Growth Stability: Part II. A Model for Critical Pitting Temperature

“…Additionally, for potentiostatic CPT measurements, the measured values and their distribution range will also be influenced by the temperature scan rate (v scan ). It was reported previously that a higher v scan will result in a high measured value of CPT 28,29 and a larger distribution range. 28 This can be addressed based on the proposed model.…”

“…It was reported previously that a higher v scan will result in a high measured value of CPT 28,29 and a larger distribution range. 28 This can be addressed based on the proposed model. According to the analysis in section 4.1, if the pitting process is completely controlled by the pit growth stability, i.e.…”

Exploration of the effect of chloride ion concentration and temperature on pitting corrosion of carbon steel in saturated Ca(OH) 2 solution

“…Over the past several decades, researchers have studied the corrosion of steel reinforcement in concrete. The reinforcement ("rebar") is made from different materials, but most commonly from carbon steel [10][11][12][13][14][15][16][17][18][19][20][21]. However, the results reported in the literature are scattered over large ranges, and the majority of them, if not all, have been limited to typical climatic temperatures and the authors are not aware of any previous work that has focused on systems at the higher temperatures and that are relevant to the disposal of HLNW in Belgium.…”