Morphological and compositional analysis of passive film on austenitic stainless steel in nitric acid medium

Passive film properties of type 304L stainless steel in nitric acid medium are investigated in both ex situ and in situ conditions. Ex situ results revealed that variation in passive film morphology occurs depending upon the concentration and time of immersion. In situ surface morphological investigation showed formation of platelet like structures at lower concentrations (0.1 M, 0.5 M), and towards higher concentration (0.6 M, 1 M) the platelet like structures got agglomerated, homogenized and started depleting from the surface leading to opening up of oxide boundaries. Compositional analysis of the passive film revealed duplex nature at lower concentration consisting of hydroxide and oxide layer, and with increasing concentration oxide layer predominates over the surface.     

Magnetoimpedance of cobalt-coated silicon steels

Magnetoimpedance (MI) effect of cobalt-coated silicon steels is measured as a function of cobalt thickness (0−45 μm), DC magnetic field (0-2 kOe), frequency (1 kHz-1 MHz) and magnitude (1-20 mA) of AC current. With increase in deposition thickness, the MI ratio and the characteristic frequency are decreased because the samples are magnetically hardened by the coating. Nevertheless, cobalt deposition broadens the frequency-dependent MI curves, and the frequency range with a large MI ratio is extended. The variations of this peak width as well as the characteristic frequency and the MI ratio are explained by the skin effect and crossing effect.     

Effects of high frequency ultrasound irradiation on incorporation of SiO2 particles within polypyrrole films

This paper deals with the effect of ultrasound on polypyrrole/SiO₂ composite film elaboration through various steps (particle dispersion, electrosynthesis). Experiments were carried out on stainless steel in phosphoric acid solution. An efficient method for dispersion of SiO₂ particles prior to electropolymerization, based on low frequency irradiation (20 kHz), was proposed. It was shown that mechanical effects of high frequency ultrasound (i.e. mass transfer improvement) led to enhancement of electropolymerization kinetics. Scanning electron microscopy imaging and glow discharge optical emission spectroscopy revealed localization of SiO₂ particles in the outer region of the films as well as better incorporation of particles under high frequency ultrasound irradiation. Finally, anticorrosion behavior of formed films was investigated in sodium chloride solution by Open Circuit Potential and anodic polarization methods. The results showed that polypyrrole/SiO₂ films elaborated under ultrasound irradiation exhibit the best protective performances.     

聚吡咯/聚苯胺复合型导电聚合物防腐蚀性能

采用循环伏安法,在含吡咯和苯胺的0.3 mol/L草酸水溶液中制备了聚吡咯/聚苯胺(PPy/Pani)的复合型导电聚合膜。采用红外光谱、极化曲线、自腐蚀电位-时间曲线、扫描电子显微镜和电化学阻抗谱研究了共聚膜的防腐蚀性能。结果表明,在1 mol/L H2SO4中,PPy、Pani与不锈钢基体发生氧化还原反应,促进不锈钢表面发生钝化;当苯胺与吡咯浓度比为1∶3时,制备得到的复合型导电聚合膜所保护的不锈钢自腐蚀电流最小,自腐蚀电位最高,保护时间最长。PPy、Pani及其共聚膜在3.5%NaCl溶液中电化学阻抗谱表明,所制备的PPy、Pani及其共聚物膜与不锈钢基体发生氧化还原反应,使其表面钝化;当Cl-到达不锈钢表面时,破坏钝化膜导致不锈钢腐蚀。     

Polydopamine supported preparation method for solid-phase microextraction coatings on stainless steel wire

In this paper, we introduced a novel and versatile route to prepare solid-phase microextraction coatings on the chemically inert stainless steel wire. Polydopamine films can be created on metallic substrates by an oxidant-induced polymerization and subsequently support various secondary reactions to prepare functional surfaces. In the present work, polydopamine-bioactivated stainless steel wire was successfully modified by nanostructured hydroxyapatite. Extraction performance of the fiber was assessed on several polycyclic aromatic hydrocarbons in water solutions. Extraction mechanism was suggested based on the correlation of partition coefficients and LogPs. Both aqueous and solid real life samples were used to test the reliability of the solid-phase microextraction-gas chromatography method; some analytes were detected and quantified.