1. A nonlinear probabilistic pitting corrosion model of Ni–Ti alloy immersed in shallow seawaterŠpiro Ivošević, Gyöngyi Vastag, Nataša Kovač, Peter Majerič, Rebeka Rudolf, 2022, original scientific article Abstract: The degradation of metal materials in a marine environment represents the consequence
of the electrochemical corrosion of metals under the influence of the environment. The application
of new materials in the maritime industry requires experimental, real-world research on the form
of corrosive damage and the intensity of the corrosion. This paper analyses the pitting corrosion of
a rod-shaped nickel–titanium (Ni–Ti) alloy that was produced by means of the continuous casting
method. In total, three samples were posted in a real seawater environment and analysed after 6,
12, and 18 months. Pits were detected on the Ni–Ti alloy after 18 months of exposure to the marine
environment. The database on pitting corrosion was created by measuring depth in mm, which was
performed by means of a nonlinear method, and by the generation of an artificial database of a total
of 120, gauged in critical pit areas. The data were obtained by the application of a nonlinear model,
and under the assumption that corrosion starts after 12 months of exposure in the corrosive marine
environment. The EDX analysis of the Ni–Ti alloy composition inside the pits and on the edges of the
pits indicated that the corrosion process in the hole of the pit occurs due to the degradation of the Ni.
Keywords: Ni–Ti alloy, pitting corrosion, seawater, EDX analysis, nonlinear, probabilistic
Published in DKUM: 24.03.2025; Views: 0; Downloads: 9
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2. Determination of the critical pitting temperature and the critical ion ($Cl^-$) concentration inducing pitting of AISI 304L stainless steel in 0.5 M $H_2SO_4$Regina Fuchs-Godec, Valter Doleček, 2004, original scientific article Abstract: Corrosion of AISI 304L stainless steel in aqueous solutions of 0.5 M $H_2SO_4$ + 0.01 M KCNS + x M NaCl was studied at different temperatures (25, 40, and 50 °C). The critical ion ($Cl^-$) concentration (CIC) and the critical pitting corrosion temperature (CPT) were determined on the basis of characteristic corrosion parameters ($i_{crit}$, $i_{pass}$, $E_{pp}$), which were obtained through potentiodynamic scanning experiments. The activation energy of the process wasfound to be equal to -42.0 (1 ± 0.08 ) kJ $mol^{-1}$. As the temperature increased, the pitting potential, $E_{pp}$, was shifted towards more negative values linearly with the reciprocal of temperature, when the concentration of added NaCl was above the CIC. In contrast, at concentrations very close to the CIC, the straight lines changed slopes. This result may indicate of the approximate boundary between metastable pitting and the beginning of stable pitting.
Keywords: austenitic stainless steel, critical ion ($Cl^-$) concetration, critical pitting corrosion temperature, metastable pitting
Published in DKUM: 10.07.2015; Views: 1233; Downloads: 113
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3. Characterization of defects in PVD TiAlN hard coatingsPeter Gselman, Tonica Bončina, Franc Zupanič, Peter Panjan, Darja Kek-Merl, Miha Čekada, 2012, original scientific article Abstract: PVD hard coatings are continuously gaining their importance in different fields of applications. In industrial use, they are often exposed to corrosive environments. Hard coatings possess inherently good corrosion resistance, but the substrate-hard coating systems may suffer from a severe corrosion attack due to the defects (craters, pin holes) in the coatings. On the sites, where defects extend through the coating, pitting corrosion can take place. These sites are drawbacks in the applications of hard coating. A PVD TiAlN hard coating was prepared on cold-work, tool-steel (AISI D2) substrates by sputtering using unbalanced magnetron sources. The growth defects incorporated into the coating were studied after the deposition and corrosion experiments. We used two methods: (1) scanning electron microscopy (SEM) for general overview of the coating topography and 2D-characterization of defects, and (2) scanning electron microscopy with a focused ion beam (SEM-FIB) for making serial cross-sections through the selected defects in order to provide images for a 3D-reconstruction of defects. In this work we tried to investigate the formation of a defect at a specific location and findout whether the selected defect causes pitting corrosion.
Keywords: trde prevleke, PVD prevleke, defekti, jamičasta korozija, mikrostruktura, PVD hard coating, defect, pitting corrosion, microstructure
Published in DKUM: 10.07.2015; Views: 1437; Downloads: 104
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4. Localized dissolution kinetics of low carbon steelAljana Petek, Valter Doleček, 2007, original scientific article Abstract: Localized dissolution of low carbon steel in saturated calcium hydroxide with different amount of sodium chloride has been investigated, using a dc technique. Potentiokinetic polarization curves indicated that pitting potentials ($E_{pit}$) decrease linearly with the log of chloride concentration. The rate of pit nucleation (1/$t_i$), and the rate of pits growth increases with increasing concentration of $Cl^-$ ions. Initiation of pitting attack could be ascribed to the adsorption of $Cl^-$ ions on the oxide surface. Adsorption of $Cl^-$ ions is physisorption and follow the Langmuir isotherm with $Δ_{ads}G^0$ = -21.1 kJ/mol.
Keywords: pitting corrosion, adsorption isotherm, low carbon steel, simulated interstitial solution
Published in DKUM: 31.05.2012; Views: 2767; Downloads: 104
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