Tracey Markley

Cerium Dibutylphosphate as a Corrosion Inhibitor for AA2024-T3 Aluminum Alloys

The suitability of cerium dibutylphosphate [Ce(dbp) 3 ] as a corrosion inhibitor for AA2024-T3 aluminum alloy in sodium chloride aqueous solutions has been investigated. Weight loss tests combined with electrochemical assessment have been used to evaluate the degree of protection and determine the inhibition characteristics of this compound. It was found that Ce(dbp) 3 offers superior protection when compared to CeCl 3 , with no discernable corrosion products, significant pitting, or evidence of replated copper on the surface. Cathodic polarization indicated inhibited oxygen reduction reaction kinetics consistent with reduced Cu replating. Corrosion protection seems to be enhanced at higher Cl - concentrations, suggesting the inhibiting film is more readily deposited when some corrosion takes place. X-ray photoelectron spectroscopy analysis of the surface confirmed the presence of both Ce(III) and Ce(IV). Focused ion beam secondary-ion mass spectroscopy (SIMS) analysis clearly indicated the presence of a 500 nm thick cerium-containing layer on the surface of the alloy after 10 days immersion in the inhibited solution. A strong phosphorus signal was also detected in the SIMS experiment. Toxicity testing using the EC-50 test suggested that cerium dibutylphosphate is able to fulfil the basic requirements for consideration as an environmentally friendly corrosion inhibitor.

Inhibition of Corrosion on AA2024-T3 by New Environmentally Friendly Rare Earth Organophosphate Compounds

Abstract The combination of rare earth metals (REM), such as Ce, La, Pr, or the less-refined mischmetal (consisting of a combination of REM) with dibutyl phosphate or diphenyl phosphate, provides a complex that shows excellent corrosion inhibition for AA2024-T3 (UNS A92024) in aqueous chloride environments. In some instances, it is equal to the inhibition provided by the chromate compounds, which are still used by the aircraft industry. The addition of these compounds as an inhibiting pigment in an epoxy coating also shows efficient suppression of filiform corrosion from scribes in the coating, under both alternate immersion and high-humidity conditions. Surface characterization of AA2024-T3 specimens immersed in solutions of these complex salts suggests that a film containing both the organic and rare earth components deposits on the alloy surface. The electrochemical data indicate that this film is acting as a mixed inhibitor, suppressing both the anodic and cathodic processes on the surface.

Influence of praseodymium - synergistic corrosion inhibition in mixed rare-earth diphenyl phosphate systems

Mixed rare-earth organophosphates have been investigated as potential corrosion inhibitors for AA2024-T3, and previously have shown synergistic inhibition behavior; however, the mechanism was not identified. In this paper, a key factor contributing to corrosion inhibition of AA2024-T3 with mischmetal diphenyl phosphate [Mm(dpp)3] is the unique stability of Pr(dpp)3 compared to other key rare earths in mischmetal. Although increasing pH causes precipitation of other components, the Pr compound is stable at higher pH. Electrochemically, a synergy is evident when Ce(dpp)3 and Pr(dpp)3 are combined. Raman mapping indicates the Pr(dpp)3 inhibitor leads to a more uniform coverage of the alloy.

Comparative study of protection of AA 2024-T3 exposed to rare earth salts solutions

Abstract The inhibitive effects of the dibutyl phosphate anion in cerium dibutylphosphate [Ce(dbp)3] on AA 2024-T351 immersed in 0·05M NaCl were evaluated by comparison with immersion in cerium chloride (CeCl3) in 0·05M NaCl as well as 0·05M NaCl alone. Scanning electron microscopy and energy dispersive X-ray hyperspectral mapping were used to examine the surfaces after exposure to the different inhibitor solutions. It was found that the dibutylphosphate anion produced additional inhibition for the matrix and the S phase intermetallic particles. The most significant mode of corrosion in the absence of inhibitors was in the form of rings of corrosion product. CeCl3 largely suppressed the formation of the rings of corrosion product, and the Ce(dbp)3 entirely eliminated them (for the time scales investigated here), indicating the additional inhibitive action of the dibutylphosphate anion.

Multifunctional rare earth organic corrosion inhibitors

All rights reserved.Chromium (VI) compounds are commonly used in paint systems to provide corrosion protection, particularly for aerospace alloys. These compounds are toxic, carcinogenic and environmentally detrimental, therefore alternatives that are safe, environmentally benign and meet or exceed current levels of corrosion protection are vital. Multifunctional rare earth organic compounds incorporate known inhibitor species, achieving synergistic inhibition in corrosive environments. The mechanism, efficiency and surface interactions of these complexes are explored. The complexes were effective inhibitors for steel and aluminium alloys, through mixed inhibition. Advantages and limitations of these inhibitor complexes, along with applications and future research direction, are discussed.