Influence of surface pretreatments on the quality of trivalent chromium process coatings on aluminum alloy

Viroulaud, Rémi; Światowska, Jolanta; Seyeux, Antoine; Zanna, Sandrine; Tardelli, Joffrey; Marcus, Philippe

doi:10.1016/j.apsusc.2017.06.246

Cited by 60 publications

(62 citation statements)

References 46 publications

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“…to the ultra-high vacuum during ToF-SIMS measurements can also suffer more important coating dehydration and formation of defects (cracking and exfoliation) [50,51] contrary to the short exposition (~10 minutes) to the law vacuum (lower than ~10 -2 mbar) during the GD-OES measurements. As presented in Figure 5 which correspond to the AA 2024 substrate meaning that the coating is thin, non-homogenous and/or present some defects as already observed previously [52]. The coverage factor by the TCP coating can be also influenced by the surface state and the surface pre-treatments of the AA 2024 substrate as also discussed previously [52].…”

Section: Accepted Manuscriptsupporting

confidence: 70%

“…As presented in Figure 5 which correspond to the AA 2024 substrate meaning that the coating is thin, non-homogenous and/or present some defects as already observed previously [52]. The coverage factor by the TCP coating can be also influenced by the surface state and the surface pre-treatments of the AA 2024 substrate as also discussed previously [52]. After PACS post-treatment (5 or 30 minutes) the Al and Cu signals are no longer observed, which suggests improved coating thickness and/or its quality (the coating more homogenous, less porous and/or defective).…”

Section: Accepted Manuscriptsupporting

confidence: 58%

“…Cr and Zr signals can be observed on the TCP coating after 0, 5 and 30 minutes of the PACS posttreatment. The XPS analysis of TCP coating was presented in details in our previous works [25,52].…”

Section: Accepted Manuscriptmentioning

confidence: 99%

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Influence of post-treatment time of trivalent chromium protection coating on aluminium alloy 2024-T3 on improved corrosion resistance

Stoica

Światowska

Romaine

et al. 2019

Surface and Coatings Technology

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Low corrosion protection performances of Trivalent Chromium Process (TCP) coatings with reference to Chromium Conversion Coatings (CCC) deposited on aluminium alloys can be overcome by application of post-treatment processes. This work shows the effect of post-treatment bath (containing hydrogen peroxide and lanthanum salt) on the chemical composition, structure and the corrosion performances of TCP coating deposited on AA 2024-T3 aluminium alloy. Different times of post-treatment bath were applied on the TCP coating and the samples were analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), X-ray Photoelectron Spectroscopy (XPS) and Glow Discharge-Optical Emission Spectrometry (GD-OES). The ToF-SIMS and GD-OES depth profiles show that the post-treatment time has no influence on the thickness of the TCP coating and on its bi-layered structure. It is composed of an outer layer, rich in zirconium and chromium oxides and an inner layer rich in aluminium oxides and oxy-fluorides. 3D ToF-SIMS images reveal an enrichment of Cr and Zr-like species over the surface of intermetallic particles with reference to alloy matrix, whereas a homogenous distribution of La is observed. The analysis of in-depth distribution shows that La is present principally in the outer part of the TCP coating. The La concentration increases with increasing post-treatment time. The effect of post-treatment time on protection was evaluated by Electrochemical Impedance Spectroscopy (EIS) and Linear Sweep Voltammetry (LSV) in a 0.001 M NaCl + 0.1 M Na 2 SO 4 electrolyte. The increased posttreatment time enhances the cathodic inhibition against oxygen reduction. The post-treatment provides improved coating homogeneity and sealing properties.

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Section: Accepted Manuscriptsupporting

confidence: 70%

Section: Accepted Manuscriptsupporting

confidence: 58%

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Influence of post-treatment time of trivalent chromium protection coating on aluminium alloy 2024-T3 on improved corrosion resistance

Stoica

Światowska

Romaine

et al. 2019

Surface and Coatings Technology

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“…Given this background, various surface treatments have been developed to improve the corrosion resistance of these alloys. Electroplating [12], anodization [13][14][15], and chemical conversion treatment [16] are representative surface treatments used industrially for many types of Al alloy. Recently, several new coating techniques have been developed for these alloys, including plasma electrolytic oxidation coating (PEO-coating) although, strictly speaking, this is an anodizing technique [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Formation of Anticorrosive Film for Suppressing Pitting Corrosion on Al-Mg-Si Alloy by Steam Coating

et al. 2018

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Al alloys offer excellent physical and mechanical properties, such as a low density, high specific strength, and good ductility. However, their low corrosion resistance has restricted their application in corrosive environments. There is a need, therefore, for a novel coating technology that is capable of improving the corrosion resistance of Al alloys. In the present study, we examined a steam-based method of forming a corrosion-resistant film on Al alloys. Al-Mg-Si alloy was used as the substrate. The cleaned substrates were set in an autoclave with ultrapure water as the steam source and processed using different temperatures and holding times, resulting in the formation of anticorrosive films on the alloy. FE-SEM images of the film surfaces showed that plate-like nanocrystals were densely formed over the entire surface. XRD patterns indicated that the film was composed mainly of AlOOH crystals. The potentiodynamic polarization curves revealed that the corrosion current density of the film-coated substrates significantly decreased, and that the pitting corrosion was completely suppressed, indicating that the corrosion resistance of the Al-Mg-Si alloy was improved by the film formed by means of steam coating.

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“…R. Viroulaud et al [24] studied the influence of surface pretreatments again on TCP over 2024-T3 aluminium alloy. They selected Sococlean A 3431 solution (provided by Socomore) as degreaser followed by pickling in Turco Smut Go NC.…”

Section: Introductionmentioning

confidence: 99%

Influence of Aerospace Standard Surface Pretreatment on the Intermetallic Phases and CeCC of 2024-T3 Al-Cu Alloy

Alba-Galvín

González-Rovira

Bethencourt

et al. 2019

Metals

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A standard three-step surface pretreatment employed in the aerospace sector for Al alloys have been investigated prior to the generation of cerium conversion coatings (CeCC) on aluminium-copper alloy 2024. Two pretreatments were analysed, one without final acid etching (Pretreatment 1) and another with this step (Pretreatment 2). Both pretreatments affect the alloy intermetallic phases, playing a key role in the development of the CeCC, and also in the susceptibility to localised corrosion in NaCl medium. Scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDX) revealed that after Pretreatment 2, Al(Cu,Mg) phases were partially or totally removed through dealloying with their subsequent copper enrichment. Conversely, none of these intermetallic phases were affected when the final acid step was not employed (Pretreatment 1). Meanwhile, Al-Cu-Fe-Mn-(Si) phases, the other major Al–Cu alloys intermetallics, suffers minor changes through the whole pretreatments chain. The protective efficiency of CeCC was evaluated using electrochemical techniques based on linear polarisation (LP) and electrochemical impedance spectroscopy (EIS). Samples with CeCC deposited after the Pretreatment 1 gave higher polarisation resistance and impedance module than CeCC deposited after Pretreatment 2. SEM-EDX and X-ray photoelectron spectroscopy analysis (XPS) indicate that the main factors explaining the corrosion resistance of the coatings is the existence of Al(Cu,Mg) intermetallics in the surface of the alloy, which promote the deposition of a cerium-based coating rich in Ce4+ compounds. These Al(Cu,Mg) intermetallics were kept in the 2024 alloy when acid etching was not employed (Pretreatment 1).

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Influence of surface pretreatments on the quality of trivalent chromium process coatings on aluminum alloy

Cited by 60 publications

References 46 publications

Influence of post-treatment time of trivalent chromium protection coating on aluminium alloy 2024-T3 on improved corrosion resistance

Influence of post-treatment time of trivalent chromium protection coating on aluminium alloy 2024-T3 on improved corrosion resistance

Formation of Anticorrosive Film for Suppressing Pitting Corrosion on Al-Mg-Si Alloy by Steam Coating

Influence of Aerospace Standard Surface Pretreatment on the Intermetallic Phases and CeCC of 2024-T3 Al-Cu Alloy

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