The effect of loading mode on the stress corrosion cracking of Zircaloy-2 in a CH3OH/HCl solution

The effect of loading mode on the susceptibility of Zircaloy-2 to stress corrosion cracking has been examined in CH3₃OH containing 0.4 vol.% of concentrated HCl. Experiments were performed under constant strain conditions using an Instron Tensile Testing Machine and a Torsion Testing device. Susceptibility was found to be much greater under tensile loading (mode I) than torsion loading (mode III), being both transgranular and intergranular in the former but only intergranular in the latter. The addition of a cathodic poison, SeO₂, increased the amount of transgranular cracking and increased susceptibility under mode I conditions while such additions had no effect under mode III conditions. The differences are interpreted as arising from absorbed hydrogen promoting transgranular cleavage while intergranular cracking is caused by dissolution.     

Degradation of corrosion resistance of Zircaloy-4 in LiOH aqueous solution

To investigate the degradation of corrosion resistance of Zircaloy-4 in LiOH aqueous solution, SIMS (secondary ion mass spectrometry) analysis was performed to examine the profiles of Li+, K+, and OH- in oxide layers formed in the same concentration (0.1 mol/L) LiOH and KOH solutions. Even though the oxide layers have an equal thickness, the penetration depth of K+ is shallower than that of Li+, and the penetration depth of OH- corroded in KOH solution is also shallower than that corroded in LiOH solution. It shows that the diffusion of OH- into oxide layer is accompanied by the corresponding cation. The difference of degradation effect of LiOH and KOH solutions on the corrosion resistance of Zircaloy-4 was discussed.     

Stress corrosion cracking of zirconium and Zircaloy-4 in halide aqueous solutions

Zirconium and Zircaloy-4 in 1 M NaCl, 1 M KBr and 1 M KI aqueous solutions were found to be susceptible to stress corrosion cracking (SCC) only at potentials above the pitting potential. In all the tested systems the following steps were found: first electrochemical breakdown of the passive film, followed by intergranular attack due to anodic dissolution assisted by stresses; and finally a fast transgranular propagation. This last step was identified as the “true” SCC process. The analysis of the possible mechanisms involved during this process led to the conclusion that the surface-mobility SCC mechanism can be used to explain the experimental results found in the present work.     

Schiff bases as corrosion inhibitor for aluminium in HCl solution

Three Schiff bases named 1,5-bis[2-(2-hydroxybenzylideneamino)phenoxy]-3-oxopentane (D1), 1,5-bis[2-(5-chloro-2-hydroxybenzylideneamino)phenoxy]-3-oxopentane (D2) and 1,5-bis[2-(5-bromo-2-hydroxybenzylideneamino)phenoxy]-3-oxopentane (D3) were synthesized and their inhibitive capabilities on the aluminium corrosion in 0.1 M HCl were investigated by means of electrochemical impedance spectroscopy, Tafel polarisation and scanning electron microscopy techniques. Results showed that, compounds under study exhibit inhibitor properties and adsorption of these compounds was found to accord with Temkin adsorption isotherm. Polarisation curves indicated that the studied Schiff bases were cathodic inhibitor and the effectiveness of these inhibitors decreased in the order of D3 > D2 > D1. Quantum chemical calculations were performed to provide further insight into the inhibition efficiencies determined experimentally.     

Measurement and prediction of residual stresses and crystallographic texture development in rolled Zircaloy-4 plates: X-ray diffraction and the self-consistent model

Complementary methods were used to analyse residual stresses and texture evolution in Zircaloy-4 sheets which had undergone cold-rolling deformation: X-ray diffraction and the self-consistent model. A modified elastoplastic self-consistent model, adapted to large deformation, was used to simulate the experimental results and showed close agreement with the experimental data. A new formulation of crystal plasticity is proposed. The influence and the role of elastoplastic anisotropy were also studied and explained in this work. Good agreement was found between experimental and predicted crystallographic textures. The contribution and the magnitude of the first- and second-order residual stresses were correctly evaluated using information from the model. Comparison between the X-ray diffraction results and the simulations confirms that prismatic slip is the main active deformation mode in this alloy under large strain.     

Phenazone and aminophenazone as corrosion inhibitors for aluminum in HCl solution

The corrosion behavior of aluminum in 1 M HCl solution in the absence and presence of phenazone and aminophenazone was investigated using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results of these techniques show that, the inhibition efficiency of these compounds depends on their concentration and chemical structure. The inhibitive action of these compounds was discussed in terms of blocking the electrode surface by adsorption of the molecules through the active centers contained in their structure. The adsorption process was found to obey Temkin isotherm model. The effect of temperature on the rate of corrosion in the absence and presence of these compounds was also, studied. Some activated thermodynamic parameters were computed and discussed. Potentiodynamic polarization data indicated that these compounds act as cathodic type inhibitors. From impedance data it is found that the corrosion of aluminum is controlled by charge transfer process at all concentrations of inhibitors. Quantum chemical parameters were constructed in order to characterize the inhibition performance of the tested molecules.     

Effect of Cefazolin on the corrosion of mild steel in HCl solution

The adsorption and inhibition effect of Cefazolin on mild steel in 1.0 M HCl at 308-338 K was studied by weight loss, EIS, potentiodynamic polarization and atomic force microscopy techniques. The results showed that inhibition efficiency increased with inhibitor concentration. The adsorption of Cefazolin on mild steel surface obeys the Langmuir adsorption isotherm equation. Both thermodynamic (enthalpy of adsorption , entropy of adsorption and free energy of adsorption ) and kinetic parameters (activation energy and pre-exponential factor A) were calculated and discussed. Polarization curves showed that Cefazolin acted as mixed-type inhibitor controls predominantly cathodic reaction.     

Stress corrosion cracking of brass in ammonia solution

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅＴＥＭｏｂｓｅｒｖａｔｉｏｎｓｓｈｏｗｅｄ[1～ 4 ] ｔｈａｔｔｈｅｃｏｒ ｒｏｓｉｏｎｐｒｏｃｅｓｓｉｔｓｅｌｆｃａｎｆａｃｉｌｉｔａｔｅｄｉｓｌｏｃａｔｉｏｎｅｍｉｓｓｉｏｎａｎｄｍｏｔｉｏｎｄｕｒｉｎｇｓｔｒｅｓｓｃｏｒｒｏｓｉｏｎｃｒａｃｋｉｎｇ(ＳＣＣ)ｏｆｂｒａｓｓ,310ｓｔａｉｎｌｅｓｓｓｔｅｅｌ,ａｎｄＴｉ3Ａｌ Ｎｂ .Ｎａｎｏ ｃｒａｃｋｏｆＳＣＣｗｉｌｌｎｕｃｌｅａｔｅｉｎａｄｉｓｌｏｃａｔｉｏｎｆｒｅｅｚｏｎｅ(ＤＦＺ)ｏｎｌｙｗｈｅｎｔｈｅｃｏｒｒｏｓ…     

Laser pulsed welding in thin sheets of Zircaloy-4

A simulation technique for the welding process design to obtain the high reliability of nuclear fuel spacer grids is presented. A finite element model of pulsed laser welding for Zircaloy-4 plate is developed, which incorporates the phase transitions and the dynamic material properties with transient temperature. The effects of pulsed laser parameters on the pool shape and welding-induced distortion are analyzed by simulations and verified by experiments. The parametric study presents that the welding induced distortions are highly dependent on the geometry of the molten zone and the heat affected zone.     

(Short communication) Degradation of corrosion resistance of Zircaloy-4 in LiOH aqueous solution

To investigate the degradation of corrosion resistance of Zircaloy-4 in LiOH aqueous solution, SIMS (secondary ion mass spectrometry) analysis was performed to examine the profiles of Li~ , K~ , and OH~- in oxide layers formed in the same concentration (0.1 mol/L) LiOH and KOH solutions. Even though the oxide layers have an equal thickness, the penetration depth of K~ is shallower than that of Li~ , and the penetration depth of OH~- corroded in KOH solution is also shallower than that corroded in LiOH solution. It shows that the diffusion of OH~- into oxide layer is accompanied by the corresponding cation. The difference of degradation effect of LiOH and KOH solutions on the corrosion resistance of Zircaloy-4 was discussed.     

Cluster type molecule as novel corrosion inhibitor for steel in HCl solution

The MOF [Ag (qox) (4-hb)] 1, was obtained at room temperature by the reaction of AgNO₃, quinoxaline (qox) and 4-hydroxy benzoate (4-hb). A cluster molecule containing two silver atoms, two qox and two 4-hb ligands is considered the basic building block of the structure of 1. 3D-network structure is created via H-bonds and π-π stacking. The MOF 1 was tested as corrosion inhibitor for carbon steel in 1 M HCl solution using potentiodynamic polarization and electrochemical impedance techniques (EIS). The polarization measurements indicated that the MOF 1 is of mixed type. The adsorption of MOF 1 obeyed Langmuir adsorption isotherm. The inhibition efficiency increased with increase in MOF 1 concentration but decreased with increase in temperature. The activation and thermodynamic parameters were calculated and discussed. Mechanism of inhibition is explained on the basis of molecular structure of the inhibitor.     

Stress corrosion crack propagation in a TiO alloy in aqueous and methanolic solutions

Stress corrosion crack propagation in a TiO alloy in aqueous NaCl and MeOH/HCl solutions has been examined in dynamic straining experiments. Crack velocity is determined by the value of the applied strain-rate. In aqueous solutions repassivation and crack arrest occur if the strain-rate falls below a certain value, designated s,. Embrittlement tests under either open circuit conditions or with applied anodic currents in Me0H/HCl solution result in 3-zone fractures: intergranular, caused by dissolution, transgranular cleavage, caused by absorbed hydrogen, and ductile fracture. The intermediate cleavage zone disappears if specimens are aged before fracture or if the intergranular dissolution rate is raised until it becomes comparable to the rate of hydrogen diffusion. Interrupted dynamic straining tests with periodic removal of solution indicated that an embrittling process occurs in stressed specimens after removal of the solution. Additions to the solutions that promote hydrogen entry into the metal increased the crack velocity while the addition of species that inhibit hydrogen entry lowered the crack velocity. Increasing the corrosion rate was shown to result either in a reduced crack velocity or an increased crack velocity, depending upon the presence in the solution of a species inhibiting hydrogen entry. It is concluded that intergranular cracking in McOH/HCl solutions occurs as a result of anodic dissolution while the transgranular cleavage observed in both aqueous and methanolic solutions is a form of slow strain-rate hydrogen embrittlement.     

The effect of some hydrazine derivatives on the corrosion of Al in HCl solution

The inhibitive effect on the corrosion of aluminium in hydrochloric acid of Girard's T and P, oxalic, malonic and succinic acid hydrazides and acetophenone G-T was studied by thermometric and weight loss measurements. Adsorption of these hydrazine derivatives leads to the formation of a monolayer of the adsorbate on the metal surface. The results indicate that all the studied compounds can be classified with the weakly adsorbed substances except acetophenone G-T which is strongly adsorbed.     

Electrochemical and XPS studies and the potential scan rate dependent pitting corrosion behavior of Zircaloy-2 in 5% NaCl solution

Electrochemical studies of Zircaloy-2 in 5% NaCl solution were carried out using polarization and electrochemical impedance spectroscopy (EIS). Scan rate dependent pitting behavior of Zircaloy-2 was observed when polarization experiments were carried out at different scan rates (5 mV/min, 50 mV/min and 500 mV/min). Polarization resistance, double layer capacitance, and the thickness of passive film were calculated from the EIS study. The slope of the Bode plot in the capacitive region showed non-ideal behaviour, suggesting formation of pits. A distribution of chloride concentration was seen at the surface of the electrode when the test solution was sampled from different parts of the sample surface and analyzed for chloride. Inclusion of chloride ions in the passive film was observed from the XPS study and the chloride concentration increases with the higher anodic polarization. The outermost layer of the passive film was rich in hydroxide and oxy-hydroxide. A bi-layer passive film structure on the alloy surface is proposed.     

Stress corrosion crack propagation in Ti-13V-11Cr-3Al alloy in methanolic solutions

Stress corrosion crack propagation in Ti-13V-11Cr-3Al alloy in a CH₃OH/HCl mixture has been investigated in constant extension rate tests. Transgranular propagation occurs by cleavage on orthogonal planes. Solution additions of As, Hg, Pt and Quinoline indicate that hydrogen absorption causes the cleavage fracture while the effect of such additions upon the corrosion rate is unimportant. Pre-exposure embrittlement experiments on unstressed specimens revealed a reversible embrittlement phenomenon exhibiting the same cleavage fracture which could be prevented by ageing specimens after exposure but prior to fracture, a result that was further evidence for the embrittling role of absorbed hydrogen.     

Effect of ultrasonic vibration on the dechromisation corrosion of a CuCr alloy in HCl solution

The effect of ultrasonic vibration on the dechromisation corrosion of a CuCr alloy in HC1 solution was studied and the corrosion mechanisms were analyzed. It is found that ultlasonic vibration reduces the dechromisation incubation time, accelerates the dechromisafion corrosion rate, decreases the temperature and concentration of HC1 solution, and when the dechromisation occurs it seriously weakens the microstmcture of dechromisation layer. It is concluded that ultrasonic vibration can accelerate destruction of the passivation film on the Cr surface and increase the activities of Cl^- and Cr.     

The effects of Aloe vera extract on corrosion and kinetics of corrosion process of zinc in HCl solution

The effect of the extract of Aloe vera leaves on the corrosion of zinc in 2 M HCl solution was studied using weight loss technique. A. vera extract inhibited the corrosion of zinc in 2 M HCl solution and the inhibition efficiency increased with increasing concentration of the extract but decreased with increasing temperature. The adsorption of the inhibitor molecules on zinc surface was in accordance with Langmuir adsorption isotherm. A first-order kinetics relationship with respect to zinc was obtained with and without the extract from the kinetics treatment of the data.