Recent developments in corrosion inhibitors based on rare earth metal compounds

Rare earth organic compounds can provide an environmentally safe and non-toxic alternative to chromates as corrosion inhibitors for some steel and aluminium applications. For steel lanthanum 4-hydroxy cinnamate offers corrosion protection and reduces the susceptibility to hydrogen embrittlement. Recent work has also indicated that it inhibits the corrosion of steel in environments containing high levels of carbon dioxide. For aluminium alloys, cerium diphenyl phosphate provides excellent corrosion inhibition in chloride environments, and reduces susceptibly to stress corrosion cracking. Furthermore, for both steel and aluminium alloys filiform corrosion can be suppressed when rare earth inhibitor compounds are added as pigments to polymer coatings. The levels of inhibition observed are thought to be due to synergistic effects between the rare earth and organic parts of these novel compounds, and are related to the various species that may be present in the complex chemical conditions that develop in solution close to a metal surface. This paper reviews some of the published research conducted by the group at Deakin University over recent years.

Inhibiting localized corrosion of aluminum and aluminum alloy by rare earth metal compounds : behaviors and characteristics observed using an electrochemically integrated multi-electrode array

An electrochemically integrated multi-electrode array namely the wire beam electrode (WBE) has been used to characterize the behavior of cerium chloride (CeCl3) and lanthanum chloride (LaCl3) in inhibiting localized corrosion of AA2024-T3 and AA1100. CeCl3 has been found to inhibit AA2024-T3 corrosion in 0.005 M sodium chloride (NaCl) solution by suppressing galvanic corrosion activities and by creating a large number of insignificant anodes. It has also been shown to inhibit localized corrosion of AA1100 in 0.5 M NaCl solution by promoting the random distribution of minor anodes. LaCl3 has been found to inhibit localized corrosion of AA2024-T3 at 1000 ppm, although its efficiency dropped significantly when its concentration decreased to 500 ppm. The addition of CeCl3 and LaCl3 to corrosion testing cells at later stages was unable to effectively suppress existing corrosion anodes.

Chemiluminescence detection of piperazine designer drugs and related compounds using tris(2,2?-bipyridine)ruthenium(III)

 An exploration of the chemiluminescence from reactions of a large number of benzyl and phenylpiperazine analytes with tris(2,2’-bipyridyl)ruthenium(III) was carried out providing information towards the emission intensity of this chemiluminescent reagent and the structure of analytes it interacts with.

Caveolin-1 Is Necessary for Hepatic Oxidative Lipid Metabolism: Evidence for Crosstalk between Caveolin-1 and Bile Acid Signaling

Caveolae and caveolin-1 (CAV1) have been linked to several cellular functions. However, a model explaining their roles in mammalian tissues in vivo is lacking. Unbiased expression profiling in several tissues and cell types identified lipid metabolism as the main target affected by CAV1 deficiency. CAV1−/− mice exhibited impaired hepatic peroxisome proliferator-activated receptor α (PPARα)-dependent oxidative fatty acid metabolism and ketogenesis. Similar results were recapitulated in CAV1-deficient AML12 hepatocytes, suggesting at least a partial cell-autonomous role of hepatocyte CAV1 in metabolic adaptation to fasting. Finally, our experiments suggest that the hepatic phenotypes observed in CAV1−/− mice involve impaired PPARα ligand signaling and attenuated bile acid and FXRα signaling. These results demonstrate the significance of CAV1 in (1) hepatic lipid homeostasis and (2) nuclear hormone receptor (PPARα, FXRα, and SHP) and bile acid signaling.

Detection of nitro-explosive compounds using derivatization and tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence

This thesis describes a novel approach towards the trace level detection of nitramine explosives, by exploring various reduction strategies and utilising ruthenium chemiluminescence. Synthesis of novel chemiluminescence compounds has been achieved, as well as the development of a detection method for determining the shelf life of ammunition.

New Compounds Bearing [M(S2O7)3]2– Anions (M = Si, Ge, Sn): Syntheses and Characterization of A2[Si(S2O7)3] (A = Na, K, Rb), A2[Ge(S2O7)3] (A = Li, Na, K, Rb, Cs), A2[Sn(S2O7)3] (A = Na, K), and the Unique Germanate Hg2[Ge(S2O7)3]Cl2 with Cationic 1∞[

The reaction of the group 14 tetrachlorides MCl4 (M = Si, Ge, Sn) with oleum (65 % SO3) at elevated temperatures led to the unique anionic complexes [M(S2O7)3]2– that show the central M atoms in coordination of three chelating S2O72– groups. The mean distances M–O within the complexes increase from 175 pm (M = Si) via 186 pm (M = Ge) up to 200 pm (M = Sn). The charge balance for the [M(S2O7)3]2– anions is achieved by alkaline metal ions A+ (A = Li, Na, K, Rb, Cs) which were implemented in the syntheses in form of their sulfates. The size of the A+ ions, i.e. their coordination requirement causes the crystallographic differences in the crystal structures, while the structure of the complex [M(S2O7)3]2– anions remains essentially unaffected. Furthermore, we were able to characterize the unique germanate Hg2[Ge(S2O7)3]Cl2 which forms when HgCl2 is added as a source for the counter cation. The Hg2+ and the Cl– ions form infinite cationic chains according to 1∞[HgCl2/2]+ which take care for the charge compensation. For selected examples of the compounds the thermal behavior has been monitored by means of thermal analyses and X-ray powder diffraction. For A being an alkaline metal the decomposition product is a mixture of the sulfates A2SO4 and the dioxides MO2, whereas Hg2[Ge(S2O7)3]Cl2 shows a more complicated decomposition. The tris-(disulfato)-silicate Na2[Si(S2O7)3] has additionally been examined by solid state 29Si and 23Na NMR spectroscopic measurements.

Recent developments in corrosion inhibitors based on rare earth metal compounds

Rare earth organic compounds can provide an environmentally safe and non-toxic alternative to chromates as corrosion inhibitors for some steel and aluminium applications. For steel lanthanum 4-hydroxy cinnamate offers corrosion protection and reduces the susceptibility to hydrogen embrittlement. Recent work has also indicated that it inhibits the corrosion of steel in environments containing high levels of carbon dioxide. For aluminium alloys, cerium diphenyl phosphate provides excellent corrosion inhibition in chloride environments, and reduces susceptibly to stress corrosion cracking. Furthermore, for both steel and aluminium alloys filiform corrosion can be suppressed when rare earth inhibitor compounds are added as pigments to polymer coatings. The levels of inhibition observed are thought to be due to synergistic effects between the rare earth and organic parts of these novel compounds, and are related to the various species that may be present in the complex chemical conditions that develop in solution close to a metal surface. This paper reviews some of the published research conducted by the group at Deakin University over recent years.©2014 Institute of Materials, Minerals and Mining.

Rare earth 4-hydroxycinnamate compounds as carbon dioxide corrosion inhibitors for steel in sodium chloride solution

A series of rare earth 4-hydroxycinnamate compounds including Ce(4OHCin)3, La(4OHCin)3, and Pr(4OHCin)3 has been synthesized and evaluated as novel inhibitors for carbon dioxide corrosion of steel in CO2-saturated sodium chloride solutions. Electrochemical measurements and surface analysis have shown that these REM(4OHCin)3 compounds effectively inhibited CO2 corrosion by forming protective inhibiting deposits that shut down the active electrochemical corrosion sites on the steel surface. Inhibition efficiency was found to increase in the order Ce(4OHCin)3 < La(4OHCin)3 < Pr(4OHCin)3 and with increase in inhibitor concentration up to 0.63 mM. Detailed insights into corrosion inhibition mechanism of these compounds in carbon dioxide environment are also provided.