Probabilistic models of corrosion rate estimation in the case of two NiTi alloys obtained by different technological processes are analysed in this paper. The depth of corrosion was measured by focused ion beam analysis on a metal surface that was not protected by an anti-corrosion coating. The samples were exposed to the influence of three different seawater environments, and empirical data were obtained in a systematic measurement procedure after 6, 12 and 18 months. Assuming that corrosion processes begin immediately after exposure of the samples to the influence of the seawater environment, and observing the corrosion rate as a random variable affected by various stochastic processes, the formed standard linear corrosion model was analysed by a statistical approach. The three best-fitted three-parameter distributions which can describe the changes in the corrosion rate for NiTi alloys exposed to the influence of the seawater environment adequately were obtained by fitting the continuous theoretical distributions. Adequate statistical tests showed similarities and differences in the behaviour of the two observed NiTi alloys from the point of view of corrosion processes caused by air, tide and sea.

This paper gives an approach to the probabilistic percent corrosion depth estimation model for the CuAlNi Shape Memory Alloy (SMA) in different marine environments. Real testing was performed for validation of the theoretical model, where CuAlNi SMAs were exposed to 6 and 12 months in different seawater environments. Focus Ion Beam (FIB) analysis was used to measure the real corrosion depth on the surfaces of tested samples. A statistical approach to the investigation of the corrosion rate of CuAlNi SMA is given, where the corrosion rate is observed as a continuous random variable described by a linear corrosion model, with the assumption that corrosion starts immediately upon alloy surfaces being exposed to the influences of the marine environment. The three best-fitted two-parameter distributions for estimating the cumulative density function and the probability density function of the random variable were obtained by applying adequate statistical tests. Furthermore, using EDX analyses, we identified the chemical composition of the corroded materials, and with the help of Principal Component Analyses, we determined which corrosion environment had the most dominant influence on the corrosion process. The research results indicated that the changeable environment in the tides had a more heterogenic chemical content, which accelerated the corrosion rate.

Lipophilicity, a very important parameter in the potential biological activities of molecules, was investigated for newly synthesized N-substituted-2-phenylacetamide derivatives. The determination was carried out in two ways: first experimentally, by applying thin-layer chromatography (TLC) on reversed-phase TLC (RPTLC) RP18F254s in the presence of one protic (methanol) and one aprotic solvent (acetonitrile) and then mathematically, by using different software packages. The intercept of the linear dependence between volume fractions of the organic solvent and the retention parameters obtained by TLC is known as the retention chromatographic constant, R_M⁰, while the slope represents the m value. In order to establish the dependences between the partition coefficient, log P as the standard measure of lipophilicity and the alternative lipophilic parameters obtained experimentally by TLC, R_M⁰ and m values, linear regression analysis and multivariate methods, cluster analysis (CA) and principal component analysis (PCA), were used. All applied methods gave approximately similar results. Although there is a linear dependence between the two chromatographic parameters, the retention constant, R_M⁰, and the m values, only R_M⁰ shows suitable similarity with the standard measure of lipophilicity of the investigated N-substituted-2-phenylacetamide derivatives at the given conditions. The existence of this resemblance proves that the chromatographic retention constant, R_M⁰, obtained by RPTLC could be successfully used for the description of lipophilicity of investigated compounds. On the other hand, the results confirmed that the applied linear regression analysis and the multivariate analysis (CA and PCA) have the ability to compare lipophilic parameters of the investigated phenylacetamide derivatives obtained in different ways.

This study investigates the potential of dandelion (Taraxacum officinale) root ethanol extract as a green corrosion inhibitor for two types of steel (TH-550 and TS-275) in a chloride-rich environment. Steel samples were chemically prepared and immersed in a 3% NaCl solution, both without and with the extract at concentrations of 0.5, 1.0, and 1.5 g/L. Morphology and composition of steel samples after 24 h in blank and inhibited solutions, examined by SEM and EDX, revealed the inhibitive effect of dandelion extract, since corrosion products were not visible on the steel surfaces after 24 h in the inhibited solution, unlike the blank steel surfaces. Based on the weight loss, dandelion extract inhibited corrosion processes of S2 in a chloride-rich environment at all examined concentrations; on the other hand, it acted as a corrosion inhibitor of S1 in 3% NaCl only at the concentrations of 1.0 and 1.5 g/L. According to corrosion current, corrosion potential and polarization resistance determined by potentiodynamic tests, dandelion root extract is a mixed corrosion inhibitor with a dominant anodic reaction, which decreases corrosion rate by adsorbing onto anodic sites and prevents steel dissolution. According to ATR-FTIR analysis, hydroxyl groups within the inulin molecule could act as the dominant metal-complexing groups. Therefore, the adsorption properties of dandelion root extract are most probably related to this specific site. Based on electrochemical impedance spectroscopy, the enhancement of corrosion resistance in the steel samples was evident in all the inhibited solutions examined compared to a pure 3% NaCl solution.