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The corrosion behavior of carbon steel with and without shelter at four test sites (four cities) in the south of Vietnam was investigated in terms of the environmental factors such as average relative humidity, rainfall, sulphur dioxide and chloride depositions, and various exposure periods. The mass losses of the specimens with shelter at four test sites were related to SO2 concentration at each site. Without shelter, the mass loss at HoChiMinh was lower than that with shelter, whereas those of the other sites were higher without shelter than with shelter. Although the corrosion behavior at HoChiMinh was difficult to explain based on the environmental factors, it was estimated from a protective corrosion products caused by a synergistic effect among SO2 concentration, rain and sunlight.

The atmospheric corrosion of marble was evaluated in terms of SO 2 concentration as air pollution and climatic factors such as rainfall, relative humidity, temperature and so on under the field exposure. Marble of calcite type (CaCO 3 ) was exposed to outdoor atmospheric environment with and without a rain shelter at four test sites in the southern part of Vietnam for 3-month, 1- and 2-year periods from July 2001 to September 2003. The thickness loss of marble was investigated gravimetrically. X-ray diffraction and X-ray fluorescent methods were applied to study corrosion products on marble. The corrosion product of marble was only gypsum (CaSO 4 · 2H 2 O) and was washed out by rain under the unsheltered exposure condition. It was found that the most substantial factors influencing the corrosion of marble were rainfall, SO 2 concentration in the air and relative humidity. Based on the results obtained, we estimated the dose–response functions for the atmospheric corrosion of marble in the southern part of Vietnam.

The stress corrosion cracking (SCC) of the commercial austenitic stainless steels type 304 and 316 was investigated as functions of strain rate, test temperature and pH in acidic chloride solutions using a slow strain rate technique. From the comparison between the parameters such as time to failure (tf), maximum stress (σm) and strain at tf (ef) obtained in inert and corrosive environments, the relationships between tfCl(corrosive)/tfW(inert), σmCl/σmW and efCl/efW versus strain rate were divided into three regions for type 304 and 316 specimens: the strain rate-dominated, SCC-dominated and corrosion-dominated regions, respectively. Furthermore, it was found that the relationship between tfCl/tfW and σmCl/σmW in the SCC-dominated region became a good straight line for the type 304 and 316 specimens irrespective of strain rate, test temperature and pH. This suggests that σmCl/σmW became the parameter for predicting tf. The results obtained were compared with those obtained from the constant load method and are discussed in terms of the formation of slip steps, dissolution current and film formation rate.

By using a constant load method and inductive coupled plasma (ICP) spectrometer, the metal dissolution and maximum stress (σmair) of type 430 ferritic stainless, and type 304 and type 316 austenitic stainless steels during stress corrosion cracking (SCC) process were investigated under a constant applied stress condition in 0.82 kmol/m3 hydrochloric acid (HCl) and 0.82 kmol/m3 acidic chloride (pH 1.0) solutions. The σmair of the specimens interrupted at various elongations up to failure under the same constant applied stress condition was measured at room temperature and air atmosphere by using an Instron type tensile machine. The metal dissolution behaviour of the stainless steels changed at the transition time (tss) in the corrosion elongation curve; that is, the dissolution rate before tss was larger than that after tss. The σmair decreased gradually with increasing elongation, but showed a rapid small reduction at tss and then decreased with elongation with a sudden reduction around fracture. The results obtained were discussed in terms of the amount of metal ions per the number of cracks, selective dissolution, reduction in cross sectional area and so on.

The stress corrosion cracking (SCC) of a commercial austenitic stainless steel type 304 was investigated as functions of chloride concentration, chromate concentration and test temperature under a constant applied stress condition in 0.82 kmol/m3 sulphuric acid solution by using a constant load method. From the dependence of the three parameters ( l ss , steady state elongation rate; tss, transition time; tf, time to failure) obtained from corrosion elongation curve on chloride/chromate concentrations and test temperature, a parameter for predicting time to failure and critical values of chromate concentration and test temperature, below which little SCC takes place, were estimated. In addition, a transgranular SCC mechanism was qualitatively inferred and then the effect of chromate and chloride on SCC behavior was discussed.

Hydrogen permeation caused by corrosion under a cyclic wet (2 h)–dry (10 h) SO 2 condition was investigated for a high strength steel of MCM 430 by using an electrochemical technique in addition to the corrosion behavior obtained from weight loss measurement and the determination of corrosion products by using X-ray diffraction method. The hydrogen content converted from hydrogen permeation current density was observed in both wet and dry periods. The origin of proton was estimated to be from (1) the hydrolysis of ferrous ions, (2) the oxidation of ferrous ions and ferrous hydroxide, and (3) hydrolysis of SO 2 and formation of FeSO 4 , but not from the dissociation of H 2 O. With respect to the determination of the corrosion products consisting of inner (adherent) and outer (not adherent) layers, the outer layer is composed of α-FeOOH, amorphous phase and γ-FeOOH, where α-FeOOH increases with the increase in the wet–dry cycle, and amorphous phase shows the reverse trend. The corrosion product in the inner layer is mainly Fe 3 O 4 with them. On the basis of the results obtained, the role of the dry or wet period, the effect of SO 2 and the corrosion process during the cyclic wet–dry periods were discussed.

The stress corrosion cracking (SCC) of a commercial austenitic stainless steel type 316 was investigated as a function of sensitizing time (3.6 ks to 1.08 Ms at a sensitizing temperature of 923 K) and test temperature (333–373 K) in 0.82 kmol/m3 hydrochloric acid (HCl) solution by using a constant load method. From the applied stress dependence of the three parameters ( l ss , steady state elongation rate, tss, transition time, tf, time to failure), the relationships between applied stress and the three parameters were divided into three regions that are dominated by either stress, SCC or corrosion. In the SCC-dominated region, the log l ss was a linear function of the logtf regardless of applied stress and test temperature for each sensitized specimens, showing that l ss became a useful parameter for prediction of tf. Furthermore, the results obtained indicated that the degree of sensitization increased with increasing sensitizing time, reached a maximum at a sensitizing time of around 360 ks and then began to decrease at 1.08 Ms by Cr healing. On the basis of the results obtained, the effect of sensitizing time on SCC and the IGSCC mechanism were discussed.

The stress corrosion cracking (SCC) of a commercial austenitic stainless steel type 316 was investigated as a function of sensitizing temperature (800–1300 K) and test temperature (333–373 K) in 0.82 kmol/m 3 sulphuric acid solution by using a constant load method, to compare with that already obtained in 0.82 kmol/m 3 hydrochloric acid solution. The three parameters ( l ss , steady state elongation rate, t ss , transition time, t f , time to failure) were obtained from corrosion elongation curve and were divided into three regions of applied stress, irrespective of sensitizing temperature, which are dominated by either stress, SCC or corrosion. In the SCC-dominated region, the logarithm of l ss was a linear function of the logarithm of t f regardless of applied stress and test temperature for each sensitized specimens, showing that l ss became a useful parameter for prediction of t f , although the slope depended upon sensitizing temperature. The maximum applied stress, the minimum applied stress and the value of t ss / t f in the SCC-dominated region depended upon sensitizing temperature. Specifically, at a sensitizing temperature of around 950 K the maximum applied stress was smaller at a test temperature of 353 K, but larger at a test temperature of 333 K than that of the solution annealed specimens. In addition, sulphate ions were found to become more aggressive than chloride ions for the SCC susceptibility of the specimens with the most severe sensitization. On the basis of the results obtained, the effect of sensitization on SCC, the role of sulphate ions and an intergranular mechanism were discussed in comparison to the results of the sensitized specimens obtained in 0.82 kmol/m 3 HCl solution.

The stress corrosion cracking (SCC) of a commercial austenitic stainless steel type 316 was investigated as a function of sensitizing temperature (750–1300 K) and test temperature (333–373 K) in 0.82 kmol/m 3 hydrochloric acid (HCl) solution by using a constant load method. From the applied stress dependence of three parameters ( i ss : steady state elongation rate, t ss : time interval of SCC-dominated failure, t f : time to failure), the relationships between applied stress and the three parameters were divided into three regions that are dominated by either stress, SCC or corrosion. In the SCC-dominated region, the logarithm of i ss was a linear function of the logarithm of t f irrespective of applied stress and test temperature, although its slope depended upon sensitizing temperature. This result showed that the i ss became a useful parameter for prediction of t f as well as the case of the solution annealed specimens. Furthermore, at the most severe sensitization with a sensitizing temperature of around 1000 K, the slope of the linear function of log i ss vs. log t f showed a minimum, the value of t ss / t f was a maximum and the fracture appearance was an intergranular mode. On the basis of the results obtained, the effect of sensitization on SCC was discussed in comparison to the results for the solution annealed type 316 and a qualitative intergranular SCC (IGSCC) mechanism was inferred.