Influence of the heat exchange on the inhibiting efficiency of some heterocyclic derivatives against copper corrosion in 3.5% NaCl solutions.

The influence of the heat exchange on the inhibiting effciency of some heterocyclic derivatives against copper corrosion in 3.5 percent NaCl was studied. Tests were performed under heat exchange conditions with delltaT=60°C and the results were compared with those obtained in isothermal conditions at 35°C. The inhibiting effciency of the heterocyclic derivatives (thiadiazole, thiazoline, thiazole derivatives and 2Thioidantoine), at 10-3M and 10-4M concentration was evaluated. Some of the tested substances (in particularly 2Mercapto-5Methyl-Thiadiazole and 2Amino-5Mercapto-Thiadiazole) showed high inhibiting effciency against copper corrosion in 3.5 % NaCl solution under heat exchange conditions with deltaT=60°C

Corrosion and corrosion inhibition of Nickel in HClO4 solutions using the EQCM technique

Application of the electrochemical quartz crystal microbalance (EQCM) to the study of metal corrosion and its inhibition is rather recent. Among the advantages of this technique are its very high sensitivity and the possibility of simultaneous mass variations and voltammogram recording. These characteristics suggest the use of the EQCM for research in very low corrosion rate conditions. This paper reports the results of EQCM measurements on the corrosion inhibition rates of Ni in 0.1M HClO4, in the absence and presence of different inhibitors in free corrosion conditions, for following inhibitors: acridine (A), benzyl quinolinium chloride (BQCl), dodecyl quinolinium bromide (DDQBr), tributylbenzyl ammonium iodide (TBNI) and potassium iodide (KI). The corrosion rate was reduced considerably by KI and TBNI. DDQBr showed a good inhibitive effciency, while BQCl had only a small effect, and A stimulated corrosion of the Ni. Voltammograms at different scanning rates and the mass variation in the same solutions were recorded. Comparison of the current density and the mass changes provided the basis for a qualitative interpretation of the passivation of Ni and the mechanism of action of the different inhibitors

Study of corrosion inhibition of copper in 0.1 M NaCl using the EQCM technique

The inhibition of Cu corrosion in 0.1 M NaCl solution was studied using the EQCM technique. Some organic compounds, at 10-3 M concentration, were tested as inhibitors. The inhibiting effect of these additives was evaluated by recording the anodic and cathodic polarization curves on Cu, electroplated on quartz crystals. At the same time the mass changes of the electrode, as a function of the potential, were recorded. The formation of the protective film during immersion in distilled water or 0.1 M NaCl solution containing the inhibitors was followed by variation of the EQCM frequency. The protective characteristics of these films were evaluated by the mass variations of the electrode immersed in 0.1 M NaCl solution and by the voltammograms recorded after 1 min or 5 h immersion in 0.1 M NaCl solution. FTIR reflection spectra were recorded on Cu sheets immersed for 1 or 60 min in NaCl solution in the presence of inhibitors. They showed a very rapid interaction between metal surface and organic molecule. The results obtained allow us to conclude that EQCM technique has a valuable part to play in the interpretation of corrosion and corrosion inhibition mechanisms

Stress corrosion cracking behaviour of some aluminium-based metal matrix composites

This paper deals with the study of the corrosion behaviour of MMCs with AA 6061 or AA 2014 aluminium alloys as matrixes, under the combined action of a sustained elastic tensile stress and a corrosive environment, namely 3.5% NaCl solution. Such behaviour was compared with that exhibited by the corresponding matrixes. Gravimetric corrosion rates were evaluated after alternate exposures to 3.5% NaCl salt spray or to 3.5% NaCl solution. Micrographs of specimen sections obtained by the scanning electron microscope after the alternate exposure tests indicated the onset of stress corrosion cracking on both the AA 6061 matrix and the Al2O3p-reinforced AA 2014 composite. Electron Probe Microanalysis on the crack and pit surfaces and on the material bulk gave a contribution to determine the cause of the corrosion damage. An attempt was also done to apply the electrochemical noise analysis to evaluate the susceptibility of the various materials to stress corrosion cracking, during continuous immersions in 3.5% NaCl solution, in the presence of stress applied. The results were compared with those obtained with unstressed specimens. The tensile stress produced an increase in the corrosion rate which was clearly detected by the noise analysis. However, the concomitant presence of pitting (and in some cases of intergranular corrosion) and stress corrosion made difficult to distinguish between specimens suffering from the various localized corrosion forms