Effect of La (40H-Cin)3 on filiform corrosion of coated steel

The potential of lanthanum 4-hydroxy cinnamate to inhibit filiform corrosion on coated mild steel (AS1020) was investigated. The effectiveness and behaviour of this rare-earth inhibitor was examined with filiform corrosion scribe tests and Potentiodynamic Polarisation. The filiform scribe tests showed that lanthanum 4-hydroxy cinnamate, as a pigment in a coating, inhibited the initiation and propagation of both delamination and filiform corrosion on coated steel. The polarisation tests demonstrated that at pH 3, no significant inhibition was observed but a secondary passivation effect was present. At pH 9, inhibition on coated steel was found to be greater than that of the inhibition found at pH 6. The models of filament initiation and growth proposed by previous authors are also discussed.

Effects of corrosion inhibiting pigment lanthanum 4-hydroxy cinnamate on the filiform corrosion of coated steel

Corrosion protection by lanthanum hydroxy cinnamate (La(4OH-cin)3) in a polyurethane based varnish coating for mild steelhas been investigated. Filiform scribe tests, energy-dispersive X-ray spectroscopy (EDXS) and potentiodynamic polarisation (PP)techniques have been powerful tools to better understand the corrosion process at defects and under the coating. Filiform scribetests showed that La(4OH-cin)3, as a pigment in a coating, inhibited the initiation and propagation of both delamination and filiformcorrosion (FFC) on coated steel. The PP experiments provided an insight into the fundamental mechanism of FFC. The resultssuggest that La(4OH-cin)3 behaves as a mixed inhibitor and stifles the initiation and propagation of FFC. In this paper, the theory ofdelamination leading to FFC and the likely mechanism of inhibition by the La(4OH-cin)3 will be discussed.

Effects of multiple laser shock processing (LSP) impacts on mechanical properties and wear behaviors of AISI 8620 steel

The aim of this paper was to address the effects of multiple laser shock processing (LSP) impacts with different pulse energy on mechanical properties and wear behaviors of AISI 8620 steel. Wear analyses were conducted by means of calculation of volume loss and scanning electron microscope (SEM) of the wear surface. Surface profiles, roughness and micro-hardness were measured. The micro-structures in the surface layer of the untreated and LSPed samples (treated by multiple LSP impacts) were investigated by using transmission electron microscopy (TEM) observations. Experimental results and analyses indicated that multiple LSP impacts can remarkably improve the wear resistance of AISI 8620 steel, and the wear mechanism of multiple LSP impacts on AISI 8620 steel was also entirely revealed. The wear process of the unpolished sample subjected to multiple LSP impacts can be described as follows: the wear rate was big at the beginning of sliding dry wear, but then decreased after the micro-indention in the sample surface was polished to the disappear. This phenomenon can be attributed to the fact that multiple LSP impacts generate many micro-indents in the sample surface.

Electrochemical impedance spectroscopy and surface characterization techniques to study carbon dioxide corrosion product scales

Electrochemical impedance spectroscopy (EIS) was used to study carbon dioxide (CO2) corrosion product scales and their effects on further CO2 corrosion. Objectives were to determine the suitability of EIS for studying corrosion scales and to investigate the influence of environmental factors on scale formation. EIS provided useful information about protective abilities and electrochemical properties of corrosion scales. CO2 corrosion scales formed at high-temperature and pressure provided better protection than those formed at low-temperature and pressure. The level of protection of the scale formed at higher temperature and pressure increased with exposure time. EIS results were compared with coupon weight-loss measurements. Scales were analyzed using a combination of Fourier transform infrared (FTIR) analysis, x-ray diffraction (XRD), and electron microscopy.

Corrosion properties of a RF-magnetron-sputtered TiN coating deposited on 316L stainless steel

The effect of rf-power in the range from 100 to 200 W on the electrochemical properties of TiN coatings deposited on 316L stainless steel was investigated by using various electrochemical techniques in a 3.5-wt\% NaCl solution. Surface analyses were also conducted to analyze the coating characteristics. X-ray diffraction (XRD) and atomic force microscopy (AFM) analyses confirmed that increasing the rf-power led to a preferred orientation of the TiN(200) microstructure and decreased the surface roughness. The potentiodynamic test results confirmed the passive behavior of all of the specimens with low passive current densities and demonstrated that the effective pitting resistance of the TiN coatings increased with increasing rf-power. The electrochemical impedance spectroscopy (EIS) tests showed that the TiN films deposited with high rf-power had excellent corrosion resistance during an immersion time of 720 h due to their high total resistance and low porosity.