Innovations in Corrosion and Materials Science (Discontinued) - Volume 4, Issue 2, 2014

Most of electrochemical properties of thin materials are closely related with the microstructure of the thin films. In this paper, we review the preferred orientation dependency of metals in aqueous solutions. For example, aluminum foil etching in highly concentrated hydrochloric acid solution, etching of invar sheet for shadow masks, and texture related stress corrosion cracking of metals and alloys are discussed. All the phenomena were interpreted in terms of elastic properties of thin films and bulk materials.

Nuclear wasteforms are the first barrier preventing the release of radionuclides into environment. It is important that these forms are properly engineered to ensure that storage and disposal facilities are acting as designed. Cementation of nuclear wastes is a mature and reliable technology used to immobilise different waste types. Cementitious wasteforms are briefly discussed with focus on their containment performance. An overview of methods is given to test wasteforms leaching performance and models used.

Degradation of mechanical properties of fuel cladding materials due to hydrogen effects is a major concern in nuclear power plants. Zirconium-based alloys are the standard materials for this application. Hydrogen embrittlement is closely related to hydride formation. The addition of specific alloying elements can change the mechanisms of hydride formation and the characteristics of hydrogen embrittlement of zirconium-based cladding materials. The development of safer and more efficient cladding materials depends on the understanding of hydrogen effects on their mechanical properties. This work reviews the mechanisms of hydrogen embrittlement of zirconium and zirconium-based alloys for nuclear fuel claddings. The effects of different alloying elements are discussed. Materials selection strategy for the development of new cladding materials with increased resistance to hydrogen embrittlement is designed.

Density Functional Theory (DFT) calculations were performed on two quinoline molecules namely 2-hydroxyquinoline-3-carboxylic acid (2-HQCA) and 2-mercaptoquinoline-3- carboxylic acid (2-MQCA) to investigate their possible role as steel corrosion inhibitor. Calculations were carried out for neutral and protonated forms both in gas and aqueous phases for comparison. The quantum chemical properties and descriptors most relevant to their inhibition potentials such as EHOMO, ELUMO, Energy gap (ΔE), dipole moment (D), softness (S), hardness (η), fraction of electrons transferred (ΔN), electrophilicity (ω), total energy change (ΩT) have been calculated and compared. The interaction energy between the inhibitors and iron atom was also computed and discussed. The results from the calculations indicate that 2-MQCA should have better corrosion inhibition properties for steel than 2-HQCA. This is solely due to the substitution of O with S.

The CO2 laser welding technique was proposed as a method of joining dissimilar materials. The corrosion resistance of the joint of TP347HFG and VM12-SHC stainless steels in chloride solution was investigated. The stainless steels were butt welded. The materials were examined by electrochemical methods. The microstructure of the weld and the heat-affected zones were observed in an optical (OM) and scanning electron microscope (SEM). The X-ray fluorescence spectrometer (XRF) was used to determine variations in the main chemical elements across the fillet weld. The results showed a substantial intermixing of both substrates within the fusion zone. The joint in the environment of strong electrolytes of Cl- corrodes according to the electrochemical mechanism. The corrosion kinetic parameters for the substrates were calculated and discussed. The joint possesses medium resistance to electrochemical corrosion in relation to both steels.

Corrosion mechanisms of the submersed structures in offshore and onshore installations are complex with high degrees of interaction between the corrosion species, products and metallurgies. For better understanding of the mechanisms of the effects of co-existences of these parameters and to predict the unpredictable life of the structures, an ANN model was developed, using a series of experimental data, varying the corrosion influencing parameters viz. SO4 2-, Cl-, HCO3-, pH and temperature. Experimental data revealed that, while Cl-, HCO3 -, ions and temperature strongly influence in increasing the corrosion rate, SO4 2- ions decrease the rate. The effect of pH is different depending on its range between 4-12. Corrosion rates predicted by the ANN model in 3D graphics computed by Matlab programming, showed the interesting phenomenon of conjoint effects of multiple variables which throw new ideas of mitigation of corrosion by simply modifying the chemistry of the constituents. The morphology of the least and most degraded surfaces was studied by SEM.