Rare earth metal corrosion inhibitor protection

General uniform corrosion on pure magnesium has been drastically reduced by the use of inhibitors sueh as ehromate, dichromate, molybdate, nitrate, phosphates and vanadates that promote the formation of a protective layer, tend to retard corrosion (Ghali, 2006). Addition of substances that can form soluble complexes as tartrate, metaphosphate, etc. or insoluble salts as oxalate, carbonate, phosphate, fluoride, etc. is efficient at reducing corrosion. Adding soluble chromates, neutral fluorides or rare earth metal salts is effective in reducing magnesium-base metal corrosion (Schmutz et al, 2003). 

Abstract This chapter provides an overview of major corrosion testing and analysis techniques and their applications in corrosion inhibitor research, with a particular focus on electrochemical evaluation of corrosion protection by rare earth metal (REM) compounds. Attempts are made to discuss fundamental issues in inhibitor test design such as limitations in corrosion measurement techniques and challenges that may lead to the reporting of inaccurate corrosion rates and patterns. 

One of the most common approaches involves the application of rare earth compounds as corrosion inhibitors. In the last decade, a significant and increasing number of researchers have focused on the search for new rare earth compounds able to provide corrosion protection equivalent to or better than chromates for a wide variety of metal substrates. The first reports of the effectiveness of rare earth metal salts, for example CeClj, as cathodic corrosion inhibitors appeared in the... 

Besides the measures described in the main part of this paper, significant improvement of the corrosion resistance of a material can be obtained by use of inhibitors. In this case, good results seem to be achieved with rare earths employed in low amounts as alloying metals or as protective dense oxide coatings. The use of coatings often means the research into the best compromise between mechanical properties and corrosion resistance of the material. 

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