RE-containing metallic coatings

Additional corrosion inhibition can be used as a way to improve control over the corrosion processes on substrates protected with metallic coatings. It is very difficult to achieve direct addition of organic or inorganic iorric inhibitors to the metal. Therefore, an alloying approach was considered to irrtroduce a sorrrce of 

The RE alloying elements have been added to Zn-based sacrificial coatings on steel (Guessoum et al, 2011). Cerium salts, for example, are widely used for corrosion protection in the field of surface treatment. The reduction of dissolved oxygen or ions during the treatment induces an increase of a local pH on the surface and the precipitation of Ce oxides and/or a mixed ZnCe hydroxide (Aramaki, 2001). The inhibitive action of Ce is schematically demonstrated in Fig. 8.6. 

6 Schematic diagram of the inhibiting effect of Ce-additives to Zn-based galvanic layer (Guessoum et a ., 2011). 

7 Corrosion current density, on Galfan doped with different RE additives after 168 hours exposure to 0.1 M NaCI solution at 25°C (Rosalbino etal., 2009). Corrosion currents were obtained by converting the mass loss determined from the results of gravimetric determinations to corrosion current density using Faraday s law. 

These ion implantation sputtering techniques carmot be used on large size complex-shape substrates. Hot-dipping is also not an option for most of the alurrtinirrm alloys because of their high heat sensitivity. An attractive alternative 

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