Effects of Cu on Corrosion Resistance of Low Alloyed Steels in Acid Chloride Media

The corrosion resistance of two kinds of low alloyed steels was studied according to the test procedures for qualification of corrosion resistant steel for cargo oil tanks issued by International Maritime Organization. The results indicated that the addition of Cu improved the corrosion resistance of the NS-D36 steel to more than three times that of the conventional D36 steel in the strong acid solution containing chloride （10% NaC1, pHi0.85）. The anodic polarization behavior of the copper-bearing steel was studied by polarization curves and electrochemical impedance spectroscopy （EIS）, and alloying element Cu showed beneficial effects including an active potential range, low current density and high transfer resistance of electric charge. The rust layer was analyzed by scanning electron microscopy （SEM） and Auger electron spectroscopy （AES）, and the results pointed out that the mechanism of copper＇s benefi cial effects was based on the suppression of anodic dissolution by metallic copper re-deposition on the steel surface immersed in the strong acid chloride media.

Electrochemical Noise Analysis and Electrochemical Impedance Spectroscopy for Pure Copper in Chloride Media

The corrosion behavior of pure copper electrode exposed to artificial seawater has been studied using electrochemical noise analysis （ENA） and electrochemical impedance spectroscopy （EIS）. A diffusion process was observed for copper exposed to chloride media as indicated by the presence of a minimum phase angle over the lowest frequency range in the impedance plots. Analysis of electrochemical noise （EN） data has been collected both in time and frequency domains. Noise resistance Rn was obtained after analyzing EN data in the time domain. A good agreement was observed between Rn values and polarization resistance Rp values obtained from EIS analysis. Localization index Ii was not found to provide information concerning corrosion mechanisms. Also skewness and kurtosis for both potential and current fluctuations did not show any mechanistic information. It was concluded that ENA could detect the corrosion rate for copper exposed to chloride media, but was not found to provide information about the corrosion mechanisms.

Separation of Pd and Pt from highly acidic leach liquor of spent automobile catalysts with monothio-Cyanex 272 and trioctylamine

Platinum group metals(PGMs),especially Pd,Pt,and Rh,have drawn great attention due to their unique features.Direct separation of Pd and Pt from highly acidic automobile catalyst leach liquors is disturbed by various factors.This work investigates the effect of various parameters including the acidity,extractant concentration,phase ratio A/O,and diluents on the Pd and Pt extraction and their stripping behaviors.The results show that the Pd and Pt are successfully separated from simulated leach liquor of spent automobile catalysts with monothioCyanex 272 and trioctylamine(TOA).Monothio-Cyanex 272 shows strong extractability and specific selectivity for Pd,and only one single stage is needed to recover more than 99.9% of Pd,leaving behind all the Pt,Rh,and base metals of Fe,Mg,Ce,Ni,Cu,and Co in the raffinate.The loaded Pd is efficiently stripped by acidic thiourea solutions.TOA shows strong extractability for Pt and Fe at acidity of 6 mol·L^(–1) HCl.More than 99.9% of Pt and all of the Fe are extracted into the organic phase after two stages of countercurrent extraction.Diluted HCl easily scrubs the loaded base metals(Fe,Cu,and Co).The loaded Pt is efficiently stripped by 1.0 mol·L^(–1) thiourea and 0.05–0.1 mol·L^(–1) Na OH solutions.Monothio-Cyanex 272 and TOA can realize the separation of Pd and Pt from highly acidic leach liquor of spent automobile catalysts.