Using OCC simulation test, behavior of pitting propagation of two carbon steels for shipbuilding with different sulfide inclusions in synthetic seawater was studied. Test results showed that the zero current potential of the steel with type Ⅱ sulfide was more negative than that of the steel with type Ⅰ sulfilde; and at the same cathodic polarization potential, the anodic dissolution current of the former was greater than that of the latter. The effect of sulfide inclusions on the pitting propagation was examined by means of microanalysis. It was found that the sulfide accelerated propagation of the pit with a higher dissolution speed than that of the steel matrix. Because type Ⅱ sulfide was of the thin piece shape and presented in crowds, the dissolution along it could easily spread from one piece to another. Type Ⅰsulfide, with the shape similar to potato or cigar, presented in steel bulk separately. Such that, the dissolution around the latter couldn't spread as the former did. In addition, because typeⅡ sulfide had much larger Sv (phase boundary surface) than type Ⅰ sulfide, the corrosion propagation of the macro-pit was accelerated much more quickly by the former than by the latter.

Pure iron membranes were pre-charged with hydrogen at various current densities.Effect of hydrogen on the film formation process on iron was studied by electrochemical methods. It showed that charged hydrogen delays the film formation and enhances the dissolution rate at passive state. After hydrogen injection and film formation at different passivation potentials, the AC impedance of the passive film has been measured. The results revealed that the capacitance and adulterated concentration of the film is increased, but the flat band potential is decreased by intrinsic hydrogen. Photoelectrochemical test indicated that hydrogen does not change the semiconductor types of the film, but enhances the photocurrent and reduces forbidden band gap. The results are discussed in relation to semiconductor model, and it was found that hydrogen influences the electronic properties mainly through changing the composition of passive film.

For more knowledge of the performance of copper-bearing intrauterine devices (CuIUD), corrosion behavior of copper was examined in a simulated utcrine fluid containing serum albumin. Electrochemical polarization resistance measurements indicated that over the range of pH and desolved oxygen concentration under study the presence of serum albumin always increases the corrosion rate and the latter fluctuates according to the albumin levels. Its addition initially increased the corrosion rate, but the higher albumin level resulted in somewhat suppression of copper corrosion. Both X-Ray Diffraction(XRD0 analysis and cathodic reduction of surface film showed that, at a lower albumin concentration (<1g/L),only cuprous oxide was formed on the copper-substrated surface; however, a higher albumin concentation(>1g/L)suppressed the formation of cuprous oxide. The presence of albumin shifted the corrosion potential of copper towards negative. It could be inferred that the albumin accelerated the anodic process of copper and hence enhanced its corrosion.

Themogravimetric studies have been conducted on the corrosion behavior of pure chromium coated with NaCl deposit in air or oxygen containing water vapor at 500-700℃.Results indicated that in air or in oxygen plus water vapor, the weight gain of Cr sample was not detectable even at 700℃ due to the formation of a compact and uniform Cr2O3 protective scale. However, with a solid NaCl deposit on its surface, corrosion of pure Cr in the same environments was significantly accelerated because of the reaction of NaCl with the oxide and substrate metal. When testing temperature increased and approached the melting temperature of NaCl, the corrosion of pure Cr coated with NaCl in air or in oxygen plus water vapor became more severe. A mechanism to explain the syneigistic effect of water vapor and NaCl on the corrosion of pure Cr is proposed.

Electrochemical behavior of carbon steel in the simulated solutions containing H2S at different pH values have been investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy(EIS). The results indicated that at lower pH value, the electrode process of carbon steel was mainly controlled by anodic dissolution, the Nyquist diagrams were composed of a capacitive loop at high frequency and an inductive loop at the low frequency. With the increase in pH, the corrosion potential of carbon steel became more negative, as well as corrosion current density decreased. These changes could be attributed to the increase in pH and coverage of iron sulfide film, but a higher corrosion current was observed at pH 6.2, which was attributed to the depolarization of HS- in cathodic process. When the pH was higher than 7, the surface of corroding electrodes got into the stage of passivation because of the formation of iron oxide film. Based on the view of competitive adsorption between HS- and OH- on surface electrode, a probable reaction mechanism was suggested.

The corrosion inhibition by SADP(N-sulfonic amino-dimethylene phosphonic acid) on 0Cr13 stainless steel was studied by linear polarization and anodic polarization curve methods in 0.10mol/L H2SO4 solutions, compared with HEDP(1-hydroxyethylidene-1, 1-diphosphonic acid) and ATMP(aminotrimethylenephosphonic acid).It was found that these three phosphonic acids have remarkable inhibition effect on the corrosion of 0Cr13 stainless steel in H2SO4 solutions. The corrosion inhibiton mechanism by SADP、HEDP、ATMP on 0Cr13 was found to be the geometric blocking effect. Results showed that the adsorption of all these three phosphonic acids follows the Langmuir adsorption isotherm. The order in the corrosion inhibition effciency may be arranged as follows:ηSADP>ηATMP>ηHEDP.

Based on the EIS displays of carbon steel in three types of soil with different moisture contents at various time, the corresponding equivalent circuits were proposed respectively. The characteristics of EIS for carbon steel/soil system relate to soil corrosion morphology. When different carbon steel/soil systems have identical corrosion morphology, the characteristics of their EIS are similar. EIS of local corrosion is composed of two capacitive semi-circles and includes inductive are or diffusion impedance occasionally. Diffusion impedance is only a line without 45 because of dispersion effect. EIS of uniform corrosion is composed of a single capacitive are which includes two time constants. At the same time, the influence of moisture content on the corrosion behaviour of carbon steel in different soils was discussed.

The relationship between the electrolytic composition and the interfacial electic characteristics of the porous membrane of anodized aluminum was investigated. The pHIEP at isoelectric point of the porous membrane was equal to 9.20 in 1.0*10-2mol/L KCl solution. Pretreatment of the porous membrane was equal to 9.20 in 1.0*10-2mol/L KCl solution.Pretreatment of porous membrane with F-,PO43-,SiO32-, S2O32- and tannic acid shifted the pHIEP to 3.40,3.30,4.30,4.50 and 3.90, respectively. The change state and ionic selectivity of the membrane could be characterized by the place of its pHIEP relative to pHsol in solution. The membrane was positively changed and selectively pemeable to anions when pHsol References | Related Articles | Metrics

Erosion-corrosion of Ti and 00Cr25Ni22Mo2 stainless steel in 1mol/L H2SO4 solution was studied with the aid of a self-designed rotating apparatus. The experimental results showed that the erosion-corrosion rate of Ti and the stainless steel increased with increasing rotating speed and increasing temperature, and it approached the maximum at high rotating speed(>4.18m/s) and at high temperature(83℃、92℃).In the present experimental condition, the electrochemical factor played a more important role than the hydrodynamic factor in erosion-corrosion. The Nyquist plots for Ti and 00Cr25Ni22Mo2 stainless steel in 1mol/L H2SO4 solution presented single capacitive loops. Increase in rotating speed reduced the value of polarization resistance of both the materials, but did not change their characteristics of EIS,showing that erosion effect did not change their corrosion mechanism.