The electrochemical behavior of low carbon steel corroding in acidic simulation solutions containing H2S was investigated by electrochemical impedance spectroscopy , potentiodynamic polarization curves and observations of SEM and ADEX. The results showed that the cathodic depolarization was enhanced greatly by H+ ionized from H2S under stirring or static condition. Corrosion rate decreased with increasing pH within the investigated pH range. The transfer resistance (Rt) initially increased with immersion time up to about 8h, but then decreased sharply. At the initial stage of corrosion, the growth of sulfide film on the electrode suface abided by parabolic law, but after longer immersion, the sulfide film became loose, easily cracked and sloughed off, furthermore, the second growth of film arose. Finally, the growth of film was balanced by its dissolution in solution. Sulfide film formed under test condition was not protective enough for carbon steel.

Passivity and passive film breakdown of carbon steel in alkaline solutions containing H2S under anodic polarization have been investigated by electrochemical impedance spectoscopy. The results indicated that at the same pH value, the passivity of carbon steel in alkaline solutions is promoted by the addition of H2S. The Nyquist diagrams were composed of two capacitive loops at the initial stage of passivation, with increasing anodic polarization potential, the capacitive loop at high frequency disappeared, the carbon steel specimen got into the stage of passivation. At potentials higher than -690mV, HS- might he adsorbed on the surface of electrodes through competition with OH-, Furthermore, the passive film began to dissolve dur to the formation of ferric sulfide patches and the decrease in pH in and round the passive film faults caused by the oxidation of HS- adsorbed. When the ptential reached -635mV, the passive film was entirely brokendown.

A new polymer DETA-TU(isomolar adduct of diethylenetriamine and thiourea) was first introduced into reinforced concrete to inhibit corrosion of the embedded steel reinforcements. Its inhibition behavior and mechanism were studyied with linear polarization, Tafel polarization, EIS method either in simulated pore solution(SPS) or in real concrete. The results showed that DETA-TUwas a mixing type inhibitor. A 1% dosage was sufficient to hinder the corrosion of steel bar in SPS cntaining 0.1 mol/L NaCl. The salt endurance was increased from 0.02mol/L to 0.10mol/L. The results also showed DETA-TU and NaNO2 had a significant synergistic effect for corrosion inhibition of reinforing bar, especially at lower NaNO2 concentration. The EIS revealed the double beneficial function of DETA-TU for reinforced concrete, i.e., densifying the concrete pore structure and adsorbing on the surface of the steel reinforcement. XPS analysis showed the inhibition was concentrated at the steel/ concrete interface. The concentration gradient of DETA-TU from the steel/concrete interface and bulk concrete eas crucial for its inhibition efficiency.

Mass gain curves of Fe3Al-based alloys oxidized in static state or under external tensile stress were studied and compared with those of 0Cr25Al5. It was observed that the static oxidation resistance of Fe3Al-based alloys was similar to that of 0Cr25Al5 at olw temperature, but better than 0Cr25Al5 above 900℃;and dynamic oxidation resistance of Fe3Al-based alloys was a little worse than that of 0Cr25Al5. Mass gain of alloys was not only dependent on temperature and oxidization time, but also on external tensile stress. A dynamic oxidation equation, △w=k1t3/2+k2t1/2, was concluded, and was in accordance with the experimental results.

The relationships between corrosion of steel and environmental factors in sea water have been studied by grey relational analysis method. The main factors influencing localized corrosion depth of carbon steels and low alloy steels in sea water were found in accordance with grey relational grade and these dependence degree were also evaluated. The most important 3 environmental factors for marine corrosion of these steels included seawater tempenature, adhesion area of marine animals and plants and pH. Mean-while the evaluation factor for seawater corrosivity Q= (Yi×fi) was proposed. Here Yi refers to the above-mentioned 3 environmental factors , and fi is the grey relational grade of these factors to localized corrosion depth.

Corrosion potential of stainless steels immersed in seawater at four test sites in China for 180 days and corrosion data for 4 years were examined. Relationships between corrosion potential and seawater corrosion resistance of stainless steels were discussed.For stainless steels with high possivation tendency in seawater, their corrosion potential shifted toward positive with time, longer time was needed for the potential to become steady, and greater potential fluchuation was observed. The stainless steels with poor possivation tendency exhibited contrary results. Difference between steady potential of various stainless steels might be significant. At Qingdao, Zhoushan and Yulin, the variance of corrosion potential between 2Cr13 and HRS-3 reached over 0.8V. The order of steady corrosion resistance in seawater. Stainless steels with relatively positive steady potential were corrosion resistant and vice versa. Thus,corrosion resistance of stainless steels in seawater could be evaluated on the basis of corrosion potential measurements.

The effects of biofilms of Sulfate Reducing Bacteria(SRB) on carbon steel have been studied. API RP-38 media were used to culture SRB in batch and prepare SRB biofilms. The results show that the biofilms become thicker with the growth of SRB. Moreover, corrosion potential of the electrode varies with time. While the pH of the media with SRB changes from 7.2 to 6.0, the count of SRB in biofilms increases. The corrosion rates of carbon steel coupons covered by biofilms with different growth periods in 3% NaCl solution are remarkably distinctive. EDXA results present that the components of corrosion products in thesis and a bilfilm was prepared by bilolgical method.The corrosion rates for the three sorts of film were two films. The corrosion mechanism is mainly sttributed to acid attack.

Stress corrosion cracking(SCC) sensibility of austentic stainless steels SUS 316L in H2Ssaturated aqueous solution containing Cl- or CO32- was investigated by U bend samples. Addition of Cl- and reduction of solution pH intensified the SCC susceptibility of these two steels. But it was decreased obviously when adding 0.001mol/L Na2CO3 into the aq ueous solution especially for SUS316. Intergranular corrosion sensibility of SUS 316 was increased after sensitization heat treatment, and its SCC resistance got worse. However, SUS 316L exhibited remarkable immunity to sensitization. The SCC cracking morphology and the mechanism were also discussed.

Considering the feature of the soil, considerably complicated triphase medium, the grey system theory was introduced for the study of soil corrosion. A Grey Model GM(1,1) with the corrosion velocity instead of corrosion weight loss in soil as feature date was established. Moreover, besides the GM(1,1) based on time series, those based on non-time series with equal interval, such as polarization currents, anode area, etc, were developed, and calculation results also showed their adequacy.

The formation of tungsten alloy layer on carbon steel by double glow plasma surface alloying has been studied by means of SEM、XRD and other measurements. The surface layer so produced could he divided into three parts: deposition layer, diffusion layer and matrix. The study results showed that the deposition layer was constituted by W with body-centred cubic lattice and preferred orientation. The phase in the diffusion layer was α-Fe solid solution containing W and some carbide FeW3C was found in it. The matrix was T8 carbon steel. With the increase in deposition temperature, the microstructure of the deposition layer changed from the tapered outgrowth to the columnar form. It resulted in the increase of its corrosion-resistance, however, its wear resistance decreased.