Next Article in Journal
Effects of Fe3P Addition on Sintering Behaviors and Magnetic Properties of Fe-P Alloys Sintered at Low Temperatures
Previous Article in Journal
Global and High-Resolution Damage Quantification in Dual-Phase Steel Bending Samples with Varying Stress States
Article Menu
Issue 3 (March) cover image

Export Article

Open AccessArticle
Metals 2019, 9(3), 320; https://doi.org/10.3390/met9030320

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

1
Department of Materials Science, Metallurgical Engineering and Inorganic Chemistry, Engineering School, Universidad de Cádiz, 11519 Puerto Real (Cádiz), Spain
2
Department of Materials Science, Metallurgical Engineering and Inorganic Chemistry, Faculty of Marine and Environmental Sciences, Universidad de Cádiz, International Campus of Excellence of the Sea (CEI-MAR), 11510 Puerto Real (Cádiz), Spain
*
Author to whom correspondence should be addressed.
Received: 1 February 2019 / Revised: 1 March 2019 / Accepted: 7 March 2019 / Published: 12 March 2019
(This article belongs to the Special Issue Surface Chemistry and Corrosion of Light Alloys)
Full-Text   |   PDF [4577 KB, uploaded 18 March 2019]   |  

Abstract

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). View Full-Text
Keywords: aluminium; alloy phases; corrosion; surface pretreatments; CeCC aluminium; alloy phases; corrosion; surface pretreatments; CeCC
Figures

Graphical abstract

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
SciFeed

Share & Cite This Article

MDPI and ACS Style

Alba-Galvín, J.J.; González-Rovira, L.; Bethencourt, M.; Botana, F.J.; Sánchez-Amaya, J.M. Influence of Aerospace Standard Surface Pretreatment on the Intermetallic Phases and CeCC of 2024-T3 Al-Cu Alloy. Metals 2019, 9, 320.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Metals EISSN 2075-4701 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top