Interactions of the Components of Chromate Conversion Coating with the Constituents of Aluminum Alloy AA2024-T3

Abstract

Electrochemical techniques were employed to study the nature of individual interactions between the chemicals constituting a widely used commercial chromate conversion-coating treatment and the main constituents of AA2024-T3 alloy, namely, Al ͑99.999%͒, Al 2 Cu, Al-Al 2 Cu galvanic couple, and AA2024-T3 alloy. The samples were pretreated using chromate, ferricyanide, fluoride, tetrafluoroborate, and hexafluorozirconate, prior to electrochemical corrosion tests. The results were compared with untreated ͑control͒ samples. For the first time, the chemical interaction of aluminum with hexafluorozirconate has been studied. Maximum activation was observed in the case of hexafluorozirconate pretreatment, which also decreased the interfacial tension and increased surface wetting. The electrochemistry of the control and pretreated ͑except for hexafluorozirconate pretreatment͒ AA2024-T3 and Al 2 Cu were found to be similar. The cathodic electron transfer reaction rate for oxygen reduction was found to be enhanced by the presence of copper in the systems. The enhancement was proportional to the copper content. The cathodic reaction on all systems was inhibited by chromate. Aluminum was observed to undergo cathodic corrosion, leading to an enrichment of the surface copper content and subsequent enhancement of the cathodic electron transfer reaction.

Effect of Grain Refinement and Immersion Time on Morphology, Topography and Corrosion Resistance of CCC-Coated 7075 Al Alloy

“…The T6 refers to a multistage heat treatment involving dissolution, quenching and ageing that results in the formation of fine precipitates which reinforce the alloy. Prior to chromating, all samples underwent the following surface preparation steps: 6 , NaF and C 7 H 4 O 3 NSNa for different immersion times. The coated surfaces were rinsed in distilled water and then dried in laboratory air for 24 h. More details for the chromating procedure are presented elsewhere.…”

Advanced antistatic/anticorrosion coatings prepared from polystyrene composites incorporating dodecylbenzenesulfonic acid‐doped SiO2@polyaniline core–shell microspheres

“…Corrosion control is an important subject of interest to the modern metallic finishing industry. In the case of iron, chromate‐based organic coatings provide effective corrosion protection, but their use is limited by environmental concerns . Anodization increases the thickness of the oxide layer but does not change the porous nature of the layer .…”

“…In the case of iron, chromatebased organic coatings provide effective corrosion protection, but their use is limited by environmental concerns. 5 Anodization 6 increases the thickness of the oxide layer but does not change the porous nature of the layer. 7 Recently, layered materials such as anionic clays (e.g.…”

Development of an environmentally friendly protective coating for the depleted uranium–0.75wt.% titanium alloy

“…The impedance spectroscopy for CCC coated aluminum alloy 2024-T3 has been modeled and evaluated by Campestrini et al [18] and this group [17]. They fit a seven element circuit model to the data using only capacitors and resistors in nested branches, and the EC model contained components for both the porous layer and the barrier layer that have been shown to occur in CCCs on the AA2024-T3 aluminum alloy [19].…”