The corrosion fatigue crack growth (FCG)behaviour,the effect of applied potential on corrosion FCG rates,and the fracture surfaces were studied for high-strength low-alloy , titanium alloys and magnesium alloys. During investigation of the effect of applied potential on corrosion FCG rates,polarization was switched on for a time period in which it was possible to register the change in the crack growth rate corresponding to the open-circuit potential and to measure the crack growth rate under polarization.Due to the higher resolution of the crack extension measurement technique,the time rarely exceeded 300s.This approach made possible the observation of a non-single mode effect of cathodic polarization on corrosion FCG rates.Cathodic polarization accelerated crack growth when the maximum stress intensity(Kmax) exceeded a certain well-defined critical value characterisitic for a given material-solution combination.When Kmax was lower than the critical value,the same cathodic polarization,with all other conditions(speci-men,solution,pH,loading frequency,stress ratio,temperature,etc.)being equal,retarded or had no influence on crack growth.The results and fractographic observations suggested that the acceleration in crack growth under cathodic polarization was due to hydrogen-induced cracking(HIC).Therefore,critical values of Kmax ,as well as the stress intensity range (ΔK)were regarded as corresponding to the onset of corrosion FCG according to the HIC mechanism and designated as KHIC and ΔKHIC.HIC was the main mechanism of corrosion FCG at Kmax>KHIC(ΔK>ΔKHIC).For most of the material-solution combinations investigated,stress-assisted dissolution played a dominant role in the corrosion fatigue crack propagation at Kmax References | Related Articles | Metrics

In this work, the inhibiting mechanism of urea on AZ91D alloy in hand sweat had been investigated by the EIS and polarization curves. It has been found that urea absorbed on the surface of magnesium alloy and changed the capacity of alloy/solution interface by the EIS, polarization curve of AZ91D in different kinds of medium with and without urea. With the addition of urea, the concentration of OH- in the corrosion medium was increased. In this case, a protective film (MgO) formed on the alloy surface and the corrosion rate was decreased. Because of competitive adsorption of Cl- and OH- on the surface of AZ91D alloy, the inhibiting efficiency of urea decreased rapidly if the test solutions with Cl-.

Corrosion behavior of AZ91D alloy in lactic acid solutions with and without Cl- were discussed by EIS and polarization curves. The corrosion process of magnesium alloy in acidic solutions was controlled by three surface state variables: electrode potential(E), area of surface film of β phase (θ), and concentration of intermediate MgH2(Cm). During the corrosion process, a narrow periphery of αphase just around βphase was covered by the surface film extended from the film grown on β phase. Through this way, the α phase was partially protected. A new model was presented to describe the corrosion process of the magnesium alloy.

The atmospheric corrosion behavior of AZ91D magnesium alloy were studied by means of the outdoor exposure in Beijing atmosphere. The average corrosion rates of AZ91D were calculated by using weight loss method. Many methods, such as metallographic examination, SEM, XRD, EDS, IR were employed to analyze the surface properties (such as morphology, composition and structure) of the atmospheric corrosion products of AZ91D. The result of the outdoor exposure shows that AZ91D magnesium alloy is resistant to atmospheric corrosion, compared with A3 steel. The atmospheric corrosion of AZ91D magnesium alloy is a localized corrosion.

The cavitation corrosion behavior of 1Cr18Mn14N stainless steel in HCl solution was investigated by using a magnetostrictive-induced cavitation facility. The micrographs of damaged surfaces were observed by scanning electron microscope( SEM) and the polarization curves under quiescent and cavitating condition were measured. The influence of corrosion and hydrogen on cavitation damage was analyzed. The results showed that the resistance to cavitation corrosion of 1Cr18Mn14N stainless steel in 0.1 mol/L HCl solution was higher than that of 0Cr13Ni5Mo stainless steel. Conversely, the resistance was much worse than that of 0Cr13Ni5Mo stainless steel in 0.5mol/L HCl, because the combined action of anodic dissolution and hydrogen embrittlement accelerated the initiation and propagation of the crack on the surface of 1Cr18Mn14N and then facilitated the removal of massive materials by the propagation and connection of cracks.

By immersion test, natural environmental test( storage test, exposure test) of the high gravity tungalloy at Jiangjin and Wanning test station, and mechanical capability test and SEM fractograph analysis of tungalloy after test, the following results were gained. Tungalloy has good capability of corrosion prevention. Bonding phase of tungalloy has corrosion inclination in natural environments and trend of plasticity drop is resulted.

An anodic dissolution at potential of -550mV(vs. SCE) is applied to investigate the grooving corrosion sensitivity of J55 steel oil well casing in electric resistance welding (ERW) zone. The grooving corrosion sensitivity coefficient α of three types of the ERW casings after polarized for 144h in 3.5% NaCl solution depends intensively on the carbon content of J55 steel. The grooving corrosion sensitivity rises as the carbon content of the steel increases. The simulated heat treatment after ERW welding can decrease the α value to some extent, and the annealing treatment with enough time below the phase transformation point reduces the α value of ERW casing considerably. The corrosive solution and test temperature have no apparent effects on the grooving corrosion sensitivity coefficient.

The changes of chemical state for localized corrosion of iron artifacts in 3.5% NaCl solution were studied within a simulated occluded cell. As anodic currents passed the cell a series of changes took place, the most important ones were pH fall and Cl- migration within the occluded cell. It was found that as anodic currents passing the cell, the pH value fell quickly at the beginning while slowly after it about 5, which was proportional to the logarithm of quantity of passing electricity. Meanwhile the Cl- migrated into occluded cell. The quantity of Cl- migration and enrichment multiples increased with the time of current flowing. As a rule, a linear relationship existed between the amount of Cl- migration and quantity of electricity passing. Consequently, Cl- concentration was a function of pH in occluded cell.

The Fe-Al intermetallic coatings have been prepared by high velocity arc spraying (HVAS) technology on 20G steel and the oxidation performance of Fe-Al coatings has been studied. The results demonstrate that the kinetics curve of oxidation approximately follows the logarithmic law and oxidation velocity of Fe-Al coatings is less than that of 20G steel after 5 hours. The composition of the oxidized coating is composed of Al2O3, Fe2O3, Fe3O4 and FeO. These phases distribute unevenly. The protective Al2O3 film firstly forms and preserves the coatings from further oxidation.

The deformation induced martensite in metastable austenite stainless steels effects their physical and chemical properties. Worn metastable austenite stainless steel was treated with electric pulse of anode 60s-280s + cathode 30s-280s for 9h. XRD analyge, microhardness test, corrosion potential test and metallographic observation were used to analyze the amount of martensite , surface hardness and corrosion resistance before and after the treatment. The results show that the amount of martensite always decreases after the treatment. According to the various pulse width, the treatment can induce electrochemical annealing, it can also cause the priority corrosion of martensite. When electrochemically induced annealing happens, the treatment can not only keep the high hardness after the amount of martensite decreases, but also promote the corroson resistance of the stainless steel in Cl- containing solution.

The corrosion product on the surface of silver was analyzed by means of XPS. The results indicated that the unqualification of silver strip corrosion of jet fuel was caused by the active sulfides. The anticorrosion property and thermal stability of inhibitor have been investigated, the influence of the inhibitor on thermal oxidation stability of jet fuels, wear performance and water separation characteristics was investigated. The anti-corrosion mechanism for the inhibitor was studied, the reaction of DMTD derivative with the active sulfides in oil phase produce non active sulfides, thus, the silver strip corrosion was inhibited.