Potentiodynamic scan polarization curves were used to study the local corrosion of 304 stainless steel in neutral solution of 0.5 m ol/L NaCl containing various anions and concentration(MoO2-4、WO2- 4、C12H25SO-4 and C12H25C6H4SO-3)at 50℃ ,and indicated the retardation influence and inhibitor effect of the induction a nd propagation of the local corrosion of anions to stainless steel.It was found that,when anions added into the bulk solution,they retarded the local corrosion of stainless steel in the solution.Retardation effect was WO2-4＞MoO 2-4＞C12H25SO-4＞C12H25C6H4SO-3.

The effect of Al addition on the corrosion properti es of TiN coating was studied by electrochemical methods and surface analysis su ch as SEM and STM.It has been revealed that the structure of TiN coating has bee n changed from cylinder crystal to the crystal in nanometer.The corrosion proper ty of TiN and (Ti,Al)N coatings are different.The general corrosion occurred on (Ti,Al)N coating in acid and salt solution,however,the corrosion behavior of TiN coating is similar to pit corrosion.The corrosion resistance of (Ti,Al)N has be en improved for the self-repaired function of the (Ti,Al)N coating.The catal ytic process under the (Ti,Al)N coating is not as serous as that under TiN co ating.

The potentiodynamic and electrochemical impedance t echniques were employed to study the electrochemical characteristics of CO2 co rrosion of two kinds of well tube steels with corrosion scales.The results showe d that after corrosion scale formed on well tube steels,corrosion curre nt density would decrease observably,the character of Warburg impedance could be found in electrochemical impedance spectra and the protection of corrosion scal e of Cr-containing well tube steel was better than N80 steel mainly because the porosity of Cr-containing well tube steel was lower then that of N80 steel.Becau se of the pitting electrode process of N80 steel,the capacitance loop would pres ent itself in EIS at low frequency range.

Effect of 6 soluble salts on under film corrosion of metal and failure of the coatings were studied by means of exposed samples.The results show that the acceleration of NaCl to corrosion of zinc substrate is les s than that of Na2SO4 and similar with that of Na2SO3 and FeSO4.NaNO 3 acceleates greatly blistering of the coatings and affects relatively less the corrosion of the substrate.ZnCl2,however,has no harmful effects either on corr o sion of the zinc substrate or on failure of the coatings,and even has some inhib iting effect on corrosion of the substrate.The reason may be that the corrosion product when there is ZnCl2 is unsoluble Zn5(OH)8Cl2.The order that solu ble salts accelerate underfilm corrosion is as:Na2SO4≈Na2SO3＞NaCl≈FeS O4＞NaNO3ZnCl2;while the order of accelerating blistering is as:NaNO3 ≈Na2SO4＞ NaCl＞FeSO4≈Na2SO3ZnCl2.Polyurethane coating provides better pro tection than alkyd coating.Because the polarity of the molecule of polyurethane is greater than that of alkyd,the polyurethane coating can provide greater resis tance to O2 than alkyd coating.FTIR analysis shows that H-bond is formed betwe en the water molecule and the C=O group of the coatings,and therefore the water can permeate through the coatings much faster than O2.There is intermolecular H-bond 〖JG(〗O〖ZJZ；Y〗C〖ZJLX，S〗〖SX(B-*9〗H〖〗O〖DD(〗··〖DD)〗〖SX) 〗〖ZJS〗N〖ZJZ；Y〗C〖ZJLX，X；Y〗〖SX(B-*9〗O〖〗H〖DD(〗·· 〖DD)〗〖SX)〗〖ZJX〗N〖ZJZ；Y〗O〖ZJY〗〖JG)〗 in the structure of polyurethane,so the available sites for the water mol lcules to react is less than in alkyd coating.Therefore the capacity of polyu rethane to resist water is better than that of alkyd.

The characteristics of hydrogen damages for hydroge nation reactor wall-materials,which include the structure material of 2(1/4)Cr-1 Mo and the weld overlay cladding of 309L and 347L,in original and hydrogen charg ed had been investigated.The results of slow strain rate testing(SSRT)indicated that ⅰ)Fracture stress and plasticity decrease obviously after thermal charging of hydrogen.ⅱ)For original specimens the fracture of both smooth and notched s pecimens occurred in the 347L region(except the specimen which notched in 309L r egion),but if specimens charged with hydrogen the fracture changed in 309L regio n(except the specimen which notched in 347L region).Because after thermally char ging with hydrogen the fracture stress dropped from 885 MPa to 478 MPa for 309 L and from 799.9 MPa to 564 MPa for 347L respectively.The characteristics on low frequency fatigue with short-crack had been investigated.The formula da/dN =C(ΔJ)n was used to calculate the propagation rate(da/dN) in three stages and the conditional threshold value(ΔJth)of the fati gue crack.The results showed that the ΔJth of specimen after thermal hydrogen charged dropped obviously and the da/dN increased.In addition,t he fracture morphology of SSRT and different crack propagation mechanism of low frequency fatigue in three propagation stages had been observed by SEM.

Phosphating primer and anoding chemical conversion film were measured using 3 measurement of salt spray corrosion tests,potentiosta tic anodic polarization curves and electrochemical impedance spectroscopy(EIS).I t were discovered from the result that corrosion-resistance of phosphating pri mer was still better by comparison with anoding chemical conversion film.Anoding chemical conversion film was markedly corroded but phosphating primer was as th e same as original state in 10 cycles of neutral salt spray corrosion tests.Corr osion-resistance of both was similar within the part of stable state and weak po caviztion,but corrosion-resistance of phosphating primer was obviously better th an anoding chemical conversion film within the part of strong polarization.Polar ization resistance (Rp) of phosphating primer was a order of magnitude hig her ghan anoding chemical conversion film on EIS.

The effect of NaCl deposition on the atmospheric co rrosion of A3 steel at 25℃ and 80%RH was investigated.The results showed that w eight loss increased with the amount of NaCl deposition,but it did not change ob viously in the presence of more amount of NaCl deposition after exposure for cer tain time.Scanning electron microscopy(SEM),electron dispersion X-ray analysis(E DAX)and X-ray photoelectron spectroscopy(XPS)were used to study the morphology,e lement composition and valence on the corrosion surface.The surfaces were obviou sly uneven,and some tiny crevices appeared in corrosion products that can help O 2 transmit to inner layer.A brief corrosion mechanism was presented to explain t he experimental observations under this condition.

Modification of amorphous Fe-W alloy deposit by 8-H Q using electrochemical method and its corrosion resistance were researched in t his paper.A film was formed on the surface of amorphous Fe-W alloy deposit after anodic oxidation in sodium borate solution containing 8-HQ,but its corrosion re sistance was poor.A stable chromatic passive film could be obtained after diamin e being added into the above solution,and passivation in a chromate system could improve the corrosion resistance of Fe-W alloy in NaCl solution.Polarization cu rves showed that the film could block the cathodic and anodic reaction.

The effects that pH of simulated acid rain on corro sion behavior of LY12 aluminum alloy was investigated by electrochemical impedan ce spectrum and polarization curves.It was found that corrosion potential shifts to less noble value with increasing pH at the lower 3.1 and shifts to more nobl e value at the higher 3.4.In the solutions with pH≤3.4,the surface film of LY12 aluminum alloy was dissolved and the thickness of surface film and film resista nce decreased with immersion time,thus corrosion rate of LY12 aluminum alloy inc reased.In the solutions with pH≥3.8,the film thickness of LY12 aluminum alloy h ad no apparent change with immersion time,the film resistance increased with imm ersion time,and thus corrosion rate decreased.The results was discussed from sur face film of LY12 aluminum alloy,adsorption of anions and corrosion products.

TP304H(0Cr19Ni9)steels with and without shot blast ing were tested in a reheater of 1000 t/h boiler for 7552 hours.The results sho w that shot blasting can decrease the thickness of oxide scale,and enhance the c ompactness of oxidation layer.Cr concentrating in the surface can prevent the ou t diffusion of Fe,and decrease the oxidation speed,thus effectively improve the steam oxidation resistance.The effects of shot blasted on oxidation mechanism ar e analyzed,and the oxidation process of the scale phase is also discussed.

The inhibition and adsorption behavior of dicyclohe xyl ammonium chromate,cyclohexyl ammonium phosphite,dicyclohexyl ammonium nitrit e and cyclohexyl ammonium carbonate was studied by electrochemical methods and i nfrared spectrum.The additions of four inhibitors in the blank solution do not h ave a big effect on the corrosion potential and cathodic reaction,only affect the anodic reaction.Dicyclohexyl ammonium chromate showed good inhibition in the corrosion of zinc whether in the bulk or under thin layer electrolyte,while cyc lohexyl ammonium carbonate has no any inhibition.The results of infrared spectru m also proved the good adsorption of dicyclohexyl ammonium chromate on the zinc surface.

The in-situ observation of hydrogen-attacked cracks healing in carbon steel had been done by high-temperature microscope.The whole cracks healing process was recorded at the same time.The results show that the c racks became obviously thinner when heated under 630℃.The escaping of methane a nd inner crack exposure on specimen surface make a certain difference between th is experiment and true condition,the analysis indicates the cracks healing tempe rature in experiment is lower than actual system.The healing of hydrogen attacke d cracks is closely related to heat diffusion of Fe and C atoms in steel.The dri ving force of crack healing results from the plastic deforming energy Es i nduced by the growth of hydrogen attacked bubbles or cracks.The critical conditi on of healing of bubbles or cracks is Es ≥2γ/r (where γ is the surface tension,r is the radius of bubbles or half length of crack).

The cyclic oxidation behavior of Al-Si coatings on the Ni-base superalloy DZ125 has been investigated,which has been corroded by ro om temperature corrosion.The results indicated that the room temperature corrosi on decreased the Al content,and increased the surface roughness of the coating.D uring the subsequent cyclic oxidation,the phase transformation of βNiAl t oγ′Ni3Al and the spallation of Al2O3 scale are accelerated.As a re sult,the oxidation resistance and lifetime of the coating are decreased.

Structures and properties of the passive films form ed on iron in aqueous environments have been the hot topic of the electrochemist ry and materials science for two centuries from discovering the passivation phen o menon.In this paper,the significance and history about the research on the passi ve film formed on iron are introduced in brief,processes and advances in researc h on the passive film formed on iron in various aqueous environments by differen t techniques are reviewed.Four different passive film models were developed in t he history of iron passivity research,but neither of them could reflect the true nature of the passive film due to the limits of the experimental techniques and methods.With the introducing of the advanced technologies and methods,the true nature of the passive film on iron and the mechanism of the corrosion prevention for iron by passivity have been understood better and better.