Corrosion cerium chloride

Although the application of WBE system described by Tan et al. in REM-based corrosion inhibitor research has not been reported, a similar multi-electrode method has been used for the evaluation and selection of REM-based corrosion inhibitors. Muster et al. described a rapid screening approach for the evaluation of candidate corrosion inhibitors including REM compounds. Garcia et al. used this multi-electrode system to study the influence of pH on corrosion inhibition of AA2024-T3 aluminum alloy in O.lMNaCl solution containing potassium dichromate, cerium dibutylphosphate and cerium chloride. 

The first paper published by Hinton et al. (1984) describes the use of cerium chloride salts as aqueous inhibitors of corrosion for 7075-T6 aliuninum alloy in a O.IM solution of aerated sodimn chloride. Three years later, the same author published a study which stated that additions of small concentrations of rare earth salts (1000 ppm of LaCl3, YCI3, PrCl, NdCl, or CeCy, to a 0.1M NaCl solution induce a decrease in the corrosion rate of AA7075 (Amott et al., 1987). The best degree of inhibition was achieved with Ce ions (Fig. 3.1) when added as chloride compounds (Hinton et al., 1986), because of the formation of a compact film of cerium oxides and hydroxides (Amott et al., 1985). 

Hamdy and Beccaria examined the influence of pre-treatment on the corrosion protection properties of a cerium chloride conversion coating [11]. If the sample was immersed in the cerium chloride solution without a preceding etching step, then cerium chloride was absorbed non-uniformly. The generation of the cerium layer took several hours due to the need for a three-step treatment, in which each step took at least 1 h. 

In a recent paper, Moutarlier et al. [15] have claimed that the use of cerium salts in sol-gel-based corrosion protection is limited due to the high solubility of the cerium ions. In all of the papers cited here, the authors limited themselves to the use of cerium chloride or cerium nitrate. In order to examine the influence of alternative anions, in the present study, cerium sulphate, cerium acetate hydrate (cerium Ac) and cerium acetylacetonate (cerium Acac) have been compared to cerium nitrate and cerium chloride. Additionally, attempts were made to limit the solubility of cerium chloride and cerium nitrate with the addition of acetylacetone to form complexes of the cerium ions. Table 10.1 gives the solubilities of the cerium compounds examined in this study. 

The cerium compounds examined in this study were selected to compare cerium compounds of different solubilities with cerium nitrate, which was proposed for corrosion protection on aluminium by Mansfeld et al. [12]. Cerium chloride and cerium nitrate are soluble in water, while cerium Ac, cerium Acac and cerium sulphate have only a limited solubility in water. According to the data from Table 10.1, the cerium compounds can be arranged in order of increasing solubility as follows ... 

In the case of cerium compounds with good solubility in the matrix such as cerium chloride and cerium nitrate, the reason for the good corrosion protection can be found in the lack of leaching into the solute. Because of the inability to leach, the coating material is not weakened, and, therefore, the barrier properties remain intact. Due to dispersion on a molecular scale, it could be expected that the pore size in these coatings would be smaller than in the case of matrix with insoluble salts which results in a denser matrix and better barrier properties (see Figs. 10.3 and 10.4). 

Cerium nitrate and cerium chloride with additions of acetylacetone are, according to the salt spray test results, the most efficient corrosion inhibitors, when used as additives to hybrid organic-inorganic coatings. This was also demonstrated by the results of the EIS measurements. Cerium nitrate and, with reservations, cerium chloride in combination with acetylacetone are, according to the salt spray test performance, possible corrosion protection additives to the hybrid coating system used in this study. 

Aramaki, K (2002). Cerium (m) chloride and sodium octylthiopropionate as an effective inhibitor mixtme for zinc in O.IM NaCl. Corrosion Science, Vol.. 44, 0une 2001), pp. 1361-1374, ISSN 0010-938X... 

The SVET was utilized to study the effect of phosphate ions and organic buffer on the corrosion of carbon steel in dilute solution of chlorides and sulfates (Franklin et al., 1992), and the influence of cerium as a cathodic inhibitor on the localized corrosion of aluminum-copper alloys (Aldyke-wicz et al., 1995). Franklin et al. (1992) in-... 

Yasakau et a/. studied the mechanism of corrosion protection of aluminum alloy 2024-T3 by cerium and lanthanum inhibitors in chloride media using SKPFM,... 

Aramaki K (2002a) Synergistic inhibition of zinc corrosion in 0.5 MNaCl by combination of cerium(ni) chloride and sodium sihcate Title , Corrosion Science, 44,4, 871-886. 

Arenas MA, de Damborenea JJ (2006a) Interference by cerium cations during the multi-step zinc dissolution process in a chloride-containing electrolyte . Corrosion Science 48,3196-3207. 

Smith et al. studied corrosion inhibition of AA2014-T6 using cerium (III) cations combined with various anions, such as chloride, glycolate, iodate, tartrate and formate however, all compounds exhibited a similar degree of corrosion inhibition and no corrrmerrt was made of any synergistic effects. 

Standard corrosion testing such as weight loss. Unear polarization resistance (LPR) and cyclic potentiodynamic polarization (CPP) were used to assess each compound s inhibition efficiency for steel in 0.01 M NaCl solution. Cerium and lanthanum combined with cinnamate and substituted cinnamates produced the most effective corrosion inhibition for steel. As an example, lanthanum 4-nitrocirmamate achieved 92% inhibition for mild steel itmnersed for 7 days in sodium chloride solution. Cerium 4-methoxycinnamate was also effective as a corrosion inhibitor. Electrochemical measurements showed the rare earth cinnamate compounds to be mixed inhibitors, with an initial suppression of anodic processes, followed by a decrease in cathodic processes after longer exposure times. 

Aramaki et al. reported on the corrosion protection of zinc using a mixture of cerium (HI) chloride (CeClj) and sodium octylthiopropionate (NaOTP) in 0.5 M NaCl. A high degree of corrosion inhibition was maintained on the treated surface after 12 days immersion (Fig. 4.10). Surface characterization showed that the... 

Ho, D.L., Apateanu, L., Deacon, G.B., Brack, N., and Forsyth, M. Assessment of the Synergy Effect of Cerium-Phosphate Compounds in Inhibiting Corrosion on AA2024-T3 Alloy in a Chloride Environment, in Corrosion and Prevention. 2002. 

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