Application of EIS to the study of corrosion behaviour of sintered ferritic stainless steels before and after high-temperature exposure

Effect of High Temperature Treatment on Aqueous Corrosion of Low-Carbon Steel by Electrochemical Impedance Spectroscopy

“…The impedance results from the diffusion of oxygen through the surface oxide scale. Previous studies have also reported that the observed capacitive behavior of such an actively corroding sample is attributable to this porous barrier layer formation [10,11]. Figure 7 presents the Nyquist diagram for the low-carbon sample treated at 675˚C.…”

“…The results clearly suggest that the effects of oxidative high temperature treatments on the corrosion behavior and surface developments of low-carbon steels, and presumably on all structural steels, is more complex than the simple expectation of increased porous surface oxide formation. For example, Bautista et al [11], in a recent study of the corrosion behavior of sintered ferritic stainless steels after high temperature (800˚C) treatment, reported that while high temperature exposures resulted in an increase in the corrosion current density for 11.3 wt.% Cr ferritic stainless steel, a similar treatment for a 16.7 wt.% Cr stainless steel sample resulted in a decrease in the corrosion current density as compared to the untreated samples.…”

Oxidation Behavior of Highly Porous Metallic Components

“…It is very difficult to calculate the real area that is exposed to oxidation because depending on the temperature and testing conditions, the pores act like open or closed porosity for the oxygen [22]. Also, formation of oxides during exposure to high temperature tends to block the small pores and reduce the irregularities of the large pores, to the point that it could significantly reduce the real area that is exposed to the attack throughout the test [24]. Logarithmic or asymptotic laws are often found when porous metals are exposed to temperatures that caused formation of amounts of oxides enough to block in short time a meaningful part of their porosity [25].…”

Spatial distribution of crystalline corrosion products formed during corrosion of stainless steel in concrete

“…The physical meaning of the components in the proposed circuit during the passive state is the following: resistance R mortar can be related to the resistance of testing solution and mortar. The first time constant parameters (resistance R 1 and constant phase element CPE 1 ) appearing at the intermediate frequencies (between 10 Hz and 10 −1 Hz) were attributed to the redox transformation which occurs on the outer region of the passive layer [23,24]. The second time constant parameters (resistance R 2 and constant-phase element CPE 2 ) appearing at the low frequencies (between 10 −1 and 10 −3 Hz) were attributed to the non-ideal interfacial capacitance of the steel surface and charge transfer resistance that reflects the corrosion resistance of the steel surface controlled by the properties of the passive film [22,24].…”

“…Because of rising nickel prices, however, new types of corrosion resistant steels with lower percentages of alloying elements have been developed, e.g., low-nickel, high-chromium corrosion-resistant steels, which can be a costeffective corrosion resistant alternative to highly alloyed stainless steels. So far, published research on these types of steel as concrete reinforcement has focused on the corrosion initiation phase, mainly on the characterization of the passive film, and on the critical conditions for the onset of corrosion [20][21][22][23][24]. Long-term research of corrosion behaviour of these steels in concrete is very scarce, especially those aiming at evaluating the real-time propagation of corrosion and the formation of corrosion products.…”