Bulk nanocrystalline ingot iron (BNII) was produced by the severe rolling technique. The corrosion behaviors of BNII and as-received conventional polycrystalline ingot iron (CPII) in 1 M HCl solution were investigated by potentiodynamic polarization tests, electrochemical impedance spectroscopy measurement, and immersion tests at room temperature. For BNII, the anodic dissolution process is inhibited, but the cathodic process is enhanced. The corrosion current and average corrosion rate of BNII are 0.479 and 0.391 those of CPII, respectively. The resistance of the charge transfer of BNII is about 1.59 times higher than that of CPII. These results indicate that the corrosion resistance of BNII is improved in comparison with CPII.

The corrosion properties of bulk nanocrystalline ingot iron (BNII) fabricated from conventional polycrystalline ingot iron (CPII) by severe rolling were investigated by means of immersion test, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) tests, and scanning electron microscopy (SEM) observation. These experimental results indicate that BNII possesses excellent corrosion resistance in comparison with CPII in acidic sulfate solution at room temperature. It may mainly result from different surface microstructures between CPII and BNII. However, the corrosion resistance of nanocrystalline materials is usually degraded because of their metastable microstructure nature, and the residual stress in nanocrystalline materials also can result in degradation of corrosion resistance according to the traditional point of view.

The Oxidation of an electro-deposited nanocrystalline Cu (nc Cu) and a conventional coarse-grain Cu (cg Cu) was investigated at 30-800 • C under 1 atm of oxygen. Both Cu samples formed external scales of copper oxide (Cu 2 O+CuO). At the lower temperature (30-300 • C) the very slow oxidation rates of both the nc and cg Cu might be attributed to the formation of a protective Cu 2 O surface layer. However at the higher temperature (300-700 • C), oxidation rates of the nc Cu were obviously faster than those of the cg Cu, which was attributed to faster diffusion of various species along grain boundaries both in the metal and in the scale. In particular, the scale grew faster on the nc Cu by means of not only rapid external oxidation as a result of outward diffusion of Cu-ions but also a significant contribution from inward diffusion of oxygen along the grain boundaries in the scales. Compared with the cg Cu, dissolved O 2 in the nc Cu may have a certain effect on the faster oxidation of the nc Cu. Above 700 • C, the difference seemed to disappear as a result of the ineffectiveness of grain-boundary diffusion.

The effect of ascorbic acid (AA) on the corrosion of mild steel in sulphuric acid solution has been investigated by open circuit potential (OCP) and polarization measurements. AA was observed to shift the OCP to more positive potentials with increasing concentration. The polarization curves revealed that AA inhibited the anodic metal dissolution reaction, although this effect became negligible at high anodic overpotentials. The trend of inhibition efficiency with concentration showed that efficiency increased rapidly at low concentrations, remained almost steady at intermediate concentrations and increased again at high concentrations. The mechanism of inhibition was considered in terms of initial chemisorption of AA according to the Temkin isotherm, followed by formation of chelate compounds with Fe 2+ ions at high concentrations. EDS and AFM analyses of the electrode surface support the proposed inhibition mechanisms.

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ilanisation treatment was proposed as a new approach for sealing treatment of microarc oxidation (MAO) coating on Mg alloy AZ91D. The morphologies of the Mg alloy surfaces after MAO with or without silanisation sealing treatment were characterised by scanning electron microscopy. The results demonstrated that quite a few structural defects, including microcracks and micropores, could be observed after MAO treatment, while most of them were able to be well sealed after silanisation treatment. Moreover, the corrosion resistance performances of the Mg alloy after surface treatments were evaluated by potentiodynamic polarisation curves and electrochemical impedance spectroscopy. The results showed that the corrosion current density of the AZ91D Mg alloy combining MAO and silanisation treatment was decreased by five orders of magnitude comparing with the untreated blank substrate, which demonstrates sharply increasing anticorrosive performances of the alloy.

Composite coatings (Ti,Al)N with different Al content were deposited on a wrought martensite steel 1Cr11Ni2W2MoV by reactive multi-arc ion plating. With the addition of Al to the coatings, the crystallographic structure of them changed from B1 NaCl to B4 ZnS, the relevant hardness and adhesive strength firstly increased then decreased and their oxidation-resistance was also dramatically improved. It was indicated that the introduction of Al was beneficial to (Ti,Al)N coatings against corrosion induced by NaCl(s) in wet oxygen at 600 °C as well as wet corrosion in NaCl solution at ambient temperature