Synthesis and Evaluation of Benzohydrazide Derivative as a Corrosion Protector for Magnesium Alloy in 3%Nacl

Inhibition action of 4-Chloro-N(3,4,5-trimethoxybenzilidene) benzohydrazide on the corrosion of magnesium alloy in alkaline medium was investigated by weight-loss technique, Nyquist spectra, Tafel plot, scanning electron microscope and energy dispersive x-ray analysis. Tafel curves of magnesium alloy showed both anodic and cathodic process suppressed. Nyquist plots, scanning electron microscope and energy dispersive x-ray analysis studies provide the confirmatory evidence for the protection of magnesium alloy by the studied inhibitor.

High rate oxygen reduction reaction during corrosion of ultra-high-purity magnesium

Comprehending the corrosion mechanism of magnesium is of major interest in diverse fields. Typically, hydrogen evolution reaction is considered as the only cathodic reaction during Mg corrosion. However, recent works demonstrate importance of considering oxygen reduction reaction (ORR) as a second cathodic process at specific conditions. With oxygen micro-optode, we show that ORR rate was higher on slower corroding ultra-high-purity Mg (UHP-Mg), while lower on faster corroding commercially pure Mg (CP-Mg), where massive hydroxide layer impeded oxygen permeation. These findings shed light on yet another facet of complex mechanism of Mg corrosion.

The Influence of KCl and HCl on the High-Temperature Oxidation of a Fe-2.25Cr-1Mo Steel at 400 °C

The influence of alkali- and chlorine-containing compounds on the corrosion of superheater alloys has been studied extensively. The current paper instead investigates the corrosive effects of KCl and HCl under conditions relevant to waterwall conditions. A low-alloy (Fe-2.25Cr-1Mo) steel was exposed to KCl(s), 500 vppm HCl(g) and (KCl + HCl) in the presence of 5%O2 and 20% H2O at 400 °C. The results indicate that alloy chlorination by KCl occurs by an electrochemical process, involving cathodic formation of chemisorbed KOH on the scale surface and anodic formation of solid FeCl2 at the bottom of the scale. The process is accompanied by extensive cracking and delamination of the iron oxide scale, resulting in a complex, convoluted scale morphology. Adding 500 vppm HCl to the experimental environment (KCl + HCl) initially greatly accelerated the formation of FeCl2 at the scale/alloy interface. The accelerated alloy chlorination is attributed to HCl reacting with KOH at the scale surface, causing the cathodic process to be depolarized. A rapid slowing down of the rate of chlorination and corrosion in KCl + HCl environment was observed which was attributed to the electronically insulating nature of the FeCl2 layer which forms at the bottom of the scale, disconnecting the anodic and cathodic regions.

Study of Corrosion Behaviour of Carbon Steel in Evian Derived Solution from Electrochemical Techniques

Marine structures and buried pipelines are constantly exposed to extreme conditions with elements such as temperature variation, soil ion content and dissolved metals posing a continuous threat on the integrity and lifespan of the structures. Quantification of these elements has been limited to studying only a few of the parameters, with the resulting corrosion behaviour not fully understood. The purpose of this study was to investigate the corrosion behaviour of carbon steel in Evian derived solution using the anodic component attained from modelled polarisation curves. The behaviour of the metal/electrolyte interface was studied using a combination of voltammetry and X-ray diffraction analysis of the mineral layer. The expression for the anodic and cathodic component of the current as a function of potential was attained from log|j| vs. potential plots. Mathematical modelling of the experimental polarisation curves was done using OriginPro Data Analysis & Graphing Software. Voltammetry around open circuit potential (VAOCP) showed the necessity for corrosion protection as the adopted electrochemical system resulted in a progressively corrosive environment. Kinetics and mechanism of the anodic and cathodic process indicated corrosion processes similar to aerated soil conditions.