A quantitative analysis based on comprehensive kinetic consideration of deformation and electro chemical hydrogen evolution reaction on crack tip surface was carried out for the effect of waveform on hydrogen evolution reaction.A new concept was proposed of dislocation transport of hydrogen atom in metal matrix interior at the crack tip.On the basis of this concept,a quantitative model was developed of the effect of waveform on hydrogen dislocation transport process.Then the relative magnitude of corrosion fatigue craCk growth rate was calculated and compared with for the three waveforms including triangle(TR), positive sawtooth(PS),and negative sawtooth(NS).Finally,experimental studies were conducted with these three waveforms for GC-4(40CrMnSiMoVA) steel in 3.5% NaCl solution by measurement of macroscopic fatigue behaviour and by observation of microscopic fracture features.It was concluded thatthe test results are in very good agreement with the predicted results.

Hot corrosion of Ti3Al, Ti3Al-Nb and TiAl intermetallic compounds in the plesence of a (Na,K)2SO4salt film at 900 and 950 ℃ in air was studied.The experimental results indicate that Ti3AI, Ti3Al-Nb and TiAl alloys suffer from severe hot corrosion. A single protective A12O3 barrier layer doest form on the alloy surface.The electrochemical mechanism is responsible for the hot corrosion,and the formation of sulfides at the alloy/scale interface may accelerate the anodic process.The addition of Nb to Ti3Al results in a significant improvement of hot corrosion resistance of the material.The corrosion resistance of TiAl is found to be superior to that of Ti3AI base alloys.

The effects of various material and environmental factors on the intergranular stress corrosion cracking(IGSCC) susceptibility of sensitixed type 304 stainless steel in NaCl solutions were studied.The repassivation potential for SCC(ER.scc) strongly depends upon the degree of sensitization of the material,NaCl concentration,testing temperature and applied stress level for the sensitized specimens.ER.scc is more negative than repassivation potential for crevice corrosion ER.CREV The range of potential leading to cracking always stud from the level equal to ER.scc and errands to higher potential levels. But no cracking occurs at potenttials below ER.scc'The applicability of the ER.scc to evaluating the susceptibilityto SCC for the sensitized 304 stainless steel has been confirmed in this study.

Studies were conducted on the stress corrosion craCking of type 304 austenitic stainless steel in acidic chloride solutions at ambient temperature by SSRT technique.Martensite etching technique and TEM were used to detect the presence of martensite phase and to relate stress corrosion craCking withthe martensite formation.The obserwtions showed that the deformation induced martensite promoted not only the initiation of stress corrosion cracks but also subsequent propagation of the cracks through martensite phase by its selective corrosion.The possible mechanism of crack propagation through the martensite phase was discussed according to the results of electrochemical measurements.

Corrosion inhibition of ATMP(aminotrimethylene phosphonic acid),MADMP(methylaminodimethy lene phosphonic acid),BADMP(n-butyl-aminodimethylene phosphonic acid) and HEDP(1-hydroxyethylidene 1,1-diphosphonic acid) for 1Cr13 stainless steel in deaerated 0.10 mol/L H2SO4 at 30℃ was studied by linear polarization method. It is found that the corrosion inhibition of these met hyle nephosphonic acidswith R-N-[CH2PO(OH)2]2 structure is much better than of urotropine(hexameth lenetetramine).They act as mixed type(ano-cathodic) corrosion inhibitors.Their adsorption obeys Langmuir isotherm equation,and the adsorption equilibrium constants are 2.67×103,0.85×103 and 0.55×103 L/mol for ATMP,MADMP and BADMP respectively.According to their contribution to corrosion inhibition,the functionalgroups in these methylenephosphonic acid molecules may be arranged as:-CH2PO(OH)2 -CH3 -nC4H9.

One of the main reasons for intergranular corrosion of austenitic stainless steel is the presence of chromium depleted zones at grain boundaries due to sensitization,which is caused by heating in a certain temperature range. In this paper, potentiostatic pulse test(PPT) has been used to detect the sensitisation of austenitic stainless steel.Compared with the convertional EPR test,the PPT test has some adVantages.It can be conducted at higher speed and with less damage to the specimen,ate.According to SEM morphologies,pitting attack is noticed on the surfaCe of the specimen after EPR test.On the contrary,PPT doesn't show up pitting attack.So PPT is a more specific method for detering sensitization than EPR.

The corrosion rate,corrosive wear rate,variations of Vicker hardness and friction coefficient of worn surfaCe and recovery time of passive film were determined for a duplex stainless steel Cr27Ni6Mo3Cu2Si in H2SO4 or H2SO4+NaCl solution. MOrphologies of traCks and debris were observed. Experimental results showed that the effect of Cl-on corrosive wear of the steel could be attributed to the embrittlement spalling of worn surface.

Acoustic emission(AE) behaviour of low-carbon steel samples,which have been attacked upon exposure to hydrogen of 18MPa at temperatures 450℃ and 500℃ for 240,480 and 720 hours respeCtively,was studied during tensile tests.The experimental results showed that hydrogen attack decreased AE activity,but the count of high amplitude AE signals increased.The AE signajs originated from intergranular fraCture caused by coalescence of the micro-bubbles or microcracks on the grain boundaries.

The chlorination behavior of preoxidized Ni-13.2Cr-0.47Ce alloy was investigated thermogravimetrically between 400℃ and 700℃ In Cl2 the formation of volatile chlorides occurred. Preoxidized samples of the Ni-Cr-Ce alloy showed better resistance against chlorination than as received samples because of the formation of protective chide scale.During chlorination at lower temperature,weight change of the alloy versus time followed parabolic rate low.Oxide scale exhibited only slight damage after long-time come sion.At medium temperatures,the chide scale aller long-time exposure,showed up a severely blistered morphology.At higher temperatures,oxide scale was destroyed even in a short time.The rate of corrosion increased rapidly and there was a linear decrease in weight with time.

Multicyclic potentiodynamic polarization(MCPDP) technique was used to rapidly evaluate the corrooion resistance of organic coat/mrtsl system.Some faCtors affecting corrosion resistance of the coated steel,such as the type Of organic coatings,film thickness,defects in the coating,chemical state at interfaCe between metal and organic coating,and cO8ting curing condition,were examined.The explicable data Of MCPDP measurements were obtained and discussed.It was further indicated that the MCPDP technique as an electrochemical method for assessing anti-corrosion performance of organic coatings may have a number of adVantages:being fast,being reliable and sensive,and simplicity in both operation and interpretation of the experimental results.