Abstract
There are many methods for incorporating organic corrosion inhibitors to oxide coatings formed on aluminum alloys. However, typically they require relatively concentrated solutions of inhibitors, possibly generating a problematic waste and/or are time-/energy-consuming (elevated temperature is usually needed). The authors propose a three-step method of oxide layer formation on 6061-T651 aluminum alloy (AAs) via alternating current (AC) plasma electrolytic oxidation (PEO), impregnation with an 8-hydroxyquinoline (8-HQ) solution, and final sealing by an additional direct current (DC) polarization in the original PEO electrolyte. The obtained coatings were characterized by scanning electron microscopy, roughness tests, contact angle measurements, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. Additionally, corrosion resistance was assessed by potentiodynamic polarization in a NaCl solution. Two types of the coating were formed (A—thicker, more porous at 440 mA cm−2; B—thinner, more compact at 220 mA cm−2) on the AA substrate. The 8-HQ impregnation was successful as evidenced by XPS. It increased the contact angle only for the B coatings and improved the corrosion resistance of both coating systems. Additional DC treatment destroyed superficially adsorbed 8-HQ. However, it served to block the coating pores (contact angle ≈ 80°) which improved the corrosion resistance of the coating systems. DC sealing alone did not bring about the same anti-corrosion properties as the combined 8-HQ impregnation and DC treatment which dispels the notion that the provision of the inhibitor was a needless step in the procedure. The proposed method of AA surface treatment suffered from unsatisfactory uniformity of the sealing for the thicker coatings, which needs to be amended in future efforts for optimization of the procedure.
Highlights
Despite its advantages, such as low density and good resistance towards atmospheric corrosion, pure aluminum is rarely used as a construction material because of its high plasticity and softness
The Plasma electrolytic oxidation (PEO) coatings were capable of rapidly soaking in the solution of 8-hydroxyquinoline in ethanol which served to uniformly distribute the substance throughout the oxide that was allowed to evaporate leaving the surface enriched with the corrosion inhibitor;
The provision of the inhibitor to the oxide layers led to the slight surface hydrophobization without influencing the surface roughness and morphology of the original coating and improved the corrosion resistance of the coating system;
Summary
Despite its advantages, such as low density and good resistance towards atmospheric corrosion, pure aluminum is rarely used as a construction material because of its high plasticity and softness. To amend these problems, aluminum is alloyed with other elements, such as copper, magnesium, zinc, or silicon to improve the features of the final material. Because of relatively high growth rates encountered in the process [7] combined with the unusual mechanism of oxide formation constituting plasma formation and quenching [4,5,8], electrolytic bath ingredients can be incorporated into the layer allowing for easy modification of the coating composition [1,3]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
