The corrosion behavior and the influence of the electrode potential on the corrosion behavior of simple Al-diffusion coating and Pt-containing Al-diffusion coating LDC-2 have been studied in a 90 mol.％ Na_2SO_4+10mol.% K_2SO_4 melt at 1173K.Both coatings exhibit a passive potential range, in which a protective oxide scale is formed on top of the coatings. The passive range of the Pt-containing coating LDC-2 is broader than that of the Pt-free coating, The Pt-free coating corrodes substantially faster in the passive range than the Pt-containing coating.The breakthrough potentials for acidic fluxing are close to each other for both coatings, but the LDC-2 type coating has significant higher resistance to basic fluxing than the Pt-free coating. The difference in basic breakthrough potentials of the coatings is approx. 400mV.The beneficial influence of Pt on the behavior of the Al-diffusion coating has also been discussed.

2 1/4-Cr-1Mo steel samples which had been tempered after quenching and normalizing were exposed to hydrogen at 13.5 to 31 MPa in the temperature range of 500° to 580℃. Previous work showed that the hydrogen attack(HA) resistance of normalized and tempered(N+T)steel was lower than that of quenched and tempered(Q+T)steel at temperatures above 500℃. The expansion rate of N+T sample was about one order of magnitude higher than that of Q+T Sample. This paper presents a systematic metallographic investigation in anattempt to correlate the difference of HA resistance with the difference in the microstructure. TEM, SEM, STEM EDAX and optical microscopical examination showed that the carbides in the N+T sample were less stable than those of the Q+T sample. As a consequence of heat treatment, the M_3C carbides in N+T sample contained less chromium than those in the Q+T sample. During exposure to high temperature and high pressure hydrogen, M_3C carbides in the N+T sample diminished with time much more quickly than those in the Q+T sample. Correspondingly M_2C carbides in the N+T sample were also less stable. This resulted in lower HA resistance of the N+T sample.

The characteristics of pitting corrosion above breakdown potential E_b are studied for AISI 304 stainless steel in the solution of 1NH_2SO_4+0.5NNaCl at 25℃. In potentiodynamic study, a linear relationship between E_b and cubic root of potential scanning rate is found. The actual value of E_b is obtained by extrapolation of the scanning rate to zero. It is about +596mV(SHE) for given conditions. Results also show that, at constant potential above E_b, the pit density first increases with time and tends afterwards to a steady state density of pits (S. S. D. P.)which is reached at a current density of 10mA/cm~2. The average deepening spewed of pits Vdp(mm/min) increases with(E-E_b) (mV) according to the equation:logVdp=-7.5+2.89log(E-E_b) The time dependence of courrent density at constant potential above E_b follows the equation:logJ=a+blogt The values of slope b are different for current densities below and above 10mA/cm~2, confirming the change in corrosion processes. It is suggested that, the resistance of passivating layers to pitting corrosion can be evaluated by E_b as well as S. S. D. P., Vdp and b at a given value of (E-E_b).

Electrochemical potentiodynamic polarization, potentiostatic and metallographic techniques were used to study the corrosion behaviour of SUS36 stainless steel in aldol condensation media(70℃). The effect of some factors, such as the concentrations of Cl~-, Fe~(3+) and electrode potential etc., were discussed.Experimental results showed that in the media of[Cl~-]<600ppm, anodic potential of 300～400mV (SCE)can effectively raise the corrosion resistance of SUS36 stainless steel.Corrosion monitoring technique of and potentiostatic anodic protection system for stainless steel installation in vinylon aldol condensation media are proposed. Some test results in practical application are also given.

The susceptibility to SCC (stress corrosion cracking)of steels with different strength levels has been investigated by measuring K_(1scc), hydrogen permeation, acoustic emission and by electronfractography. The metal/environment systems investigated were 4OCrNiMo steel in 3.5% NaCl solution at room temperature, 50Mn18Cr4MoVN steel in 36% Ca(NO_3)_2+3％NH_4NO_3 solution at room temperature and 34CrNi3Mo steel in 30% NaOH solution at 80℃. The test of the last system was conducted at open circuit potential as well as at a controlled potential of-1400mV (SCE). The results reveal that the effect of strength of steels on ehe susceptibility to SCC differs with different mechanism and cannot be gentralizedo When plastic deformation is the controlling factor, the increase of the strength of steels can improve the resistance to SCC.

The authors have measured the solubility parameter (δ) of polyester and epoxide resin and studied the relationship between solubility parameter of resins and the corrosion resistance of glass fiber reinforced plastics(FRP) in some organic solvents.The experimental results show that: (1) δ of resins can be used to estimate the corrosion resistance to organic solvents; (2)when δ of organic solvent is maintained at about 11.8 (for poorly hydrogen bonded) and 9.9 (for moderately hydrogen bonded) and 14.5(cal/cm~3]~(1/2)-(for strongly hydrogen bonded), corrosion resistance of commercial FRP will decrease; (3) in evaluating corrosion resistance, we must pay particular attention to the types of hydrogen bond, because δ of resin differs in different solvents with different types of hydrogen bond.

Cr, Dy-ions are implanted into pure iron and low carbon steel, Yb-ions into pure iron and Dy ions into stainless steel respectively. Auger electron spectra show the profiles of implanted species. The corrosion behaviour of the specimens is studied in NaAc/HAc solution by means of dynamic potential three sweep methods. It is found that the corrosion resistance of the materials is significantly enhanced by above mentioned ion implantation.

It was found that the addition of a small amount of La significantly improved the corrosion resistance of amorphous FeCr_(8.6)Ni_(12)P_(14)B_6 alloy. The addition of 0.075％ La to this alloy imparts to it moderate corrosion resistance in a 4N HCl solution(with corrosion rate less than 10~(-2)mm/year). The surface of the La-containing alloy and its counterpart sample without La addition was analysed by AES and XPS method. It can be seen that the La-containing alloy has a thinner and denser passive surface film with better corrosion resistance.