Conversion coatings earths

From the viewpoint of corrosion resistance, chromate conversion coatings still play an important role [106] even though a replacement of the toxic chromate is desirable. Rare earth metals are promising superseders for the chromium. They can be incorporated in the layers and enhance the corrosion resistance. 

Hosseini, M.G., Ashassi-Sorkhabi, H., Ghiasvand, H.A.Y., (2007). Corrosion protection of electro-galvanized steel by green conversion coatings. Journal of Rare Earths, Vol. 25, pp. 537-243, ISSN 1002-0721... 

S. Kiyota, B. Valdez, M. Stoytcheva, R. Zlatev and M. Scorr, Electrochemical study of corrosion behavior of rare earth based chemical conversion coating on aerospace aluminum alloy , J. Electrochem. Soc. 158, 666 (2009). 

I. Aziz, Q. Zhang and M. Xiang, Using EIS to evaluate anti-corrosion properties of the Sic /5A06 aluminium MMC treated by cerium conversion coatings , J. Rare Earths , 109 (2010). 

G. Kong, L. Liu, J. Lu, C. Che and Z. Zhong, Study on lanthanum salt conversion coating modified with citric acid on hot dip galvanized steel , J. Rare Earths, 28,461 (2010). 

A. Rudd, C. B. Breshn and F. Mansfeld, The corrosion protection afforded by rare earth conversion coatings applied to magnesium , Corr. Sci. 42,275 (2000). 

X. Yang, G. Wang, G. Dong, F. Gong andM. Zhang, Rare earth conversion coating on Mg-8.5 Li alloys , J. Alloys and Compounds, 487,64 (2009). 

Hughes, A.E., Gorman, J.D., Miller, P.R., Sexton, B.A., Paterson, P.J.K., et ai. Development of cerium-based conversion coatings on 2024-T3 Al alloy after rare-earth desmutting. Surface and Interface Analysis, 2004. 36(4) 290-303. 

Key words chromate conversion coatings, rare earth conversion coatings, sol-gel coatings, boehmite coatings, rare earth deoxidation, rare earth inhibitors. 

As described below, maity rare earth-based conversion coating formulations include H O as a species. H O can readily substitute for one or more waters of... 

The differences in solubilities of rare earth compounds have led to strategies for developing corrosion resistant coatings. For example, the extremely low solubility of cerium phosphates has led Heller et al. to use phosphate seals on cerium-based conversion coatings, to enhance corrosion resistance of the cerium-based conversion coatings. These approaches are discussed in more detail below. 

The first conversion coating process using rare earths was described in a provisional patent application in 1988 by Hinton and Wilson. " This application described a... 

For alutninium treatment the three most common rare earth salt solutions used for rare earth conversion coating are based on Ce(C10 )3 ... 

Many of the studies on the rare earths, particulariy cerium conversion coatings display a similar morphology across alloys, different anions and even rare earths and deposition methods. The common structure observed on these surfaces tends to be a nodular oxide as displayed inFig. 7.6, and suggests a common mechanism. 

The preferred method for obtaining a conversion coating on low-Cu alloys is by addition of complexed forms orBi complexes (Bi(EDTA) orBi(HDTA) depending on regulatory regimes). This is the basis of the activation process for the commercial process for rare earth conversion coating. ... 

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