Publication detail

Unconventional fluoride conversion coating preparation and characterization

DRÁBIKOVÁ, J. FINTOVÁ, S. TKACZ, J. DOLEŽAL, P. WASSERBAUER, J.

Original Title

Unconventional fluoride conversion coating preparation and characterization

English Title

Unconventional fluoride conversion coating preparation and characterization

Type

journal article in Web of Science

Language

en

Original Abstract

Purpose – The purpose of this paper is to compare electrochemical corrosion characteristics of conventional and unconventional fluoride conversion coating prepared on magnesium alloy. Design/methodology/approach – The chemical reaction of AZ61 with 38 wt. % hydrofluoric acid (HF) for 24 h was used as a conventional way of fluoride conversion coating preparation. The unconventionally prepared coating was created in Na[BF4] salt melt at 450 °C for 2 h. Morphology and chemical composition of prepared fluoride conversion coatings were studied with scanning electron microscopy and energy-dispersive X-ray spectroscopy. Electrochemical corrosion characteristics of the coatings were analyzed in Hank's solution using potentiodynamic tests. Findings – Both the coating preparation ways resulted in a creation of uniform conversion coatings with the same thickness (1.3 ± 0.1 m). Some defects were observed on the coatings surface; however, the defects did not reach the AZ61 surface. Electrochemical tests performed in Hank's solution at 37 °C showed an improvement of corrosion resistance of AZ61 treated with fluoride conversion coatings when compared to the untreated material. Unconventionally prepared coating reached better electrochemical corrosion characteristics when compared to the conventionally prepared coating. Originality/value – Electrochemical corrosion characteristics of AZ61 magnesium alloy can be improved with fluoride conversion coatings. Two methods are used in the literature for the coatings preparation. The conventional method is based on dipping of the coated material to the HF and the unconventional method lies in dipping of the sample to the Na[BF4] salt melt. The main purpose of the present study is to analyze the conventionally and unconventionally prepared coatings in terms of chemical analysis, morphology and material corrosion protection (electrochemical corrosion characteristics), while the data are not provided in the literature according to the authors knowledge. Very similar coatings were prepared using both the methods from the morphological and chemical composition point of view. However, unconventionally prepared coating created in Na[BF4] salt melt reached better electrochemical corrosion characteristics compared to the coating prepared in HF.

English abstract

Purpose – The purpose of this paper is to compare electrochemical corrosion characteristics of conventional and unconventional fluoride conversion coating prepared on magnesium alloy. Design/methodology/approach – The chemical reaction of AZ61 with 38 wt. % hydrofluoric acid (HF) for 24 h was used as a conventional way of fluoride conversion coating preparation. The unconventionally prepared coating was created in Na[BF4] salt melt at 450 °C for 2 h. Morphology and chemical composition of prepared fluoride conversion coatings were studied with scanning electron microscopy and energy-dispersive X-ray spectroscopy. Electrochemical corrosion characteristics of the coatings were analyzed in Hank's solution using potentiodynamic tests. Findings – Both the coating preparation ways resulted in a creation of uniform conversion coatings with the same thickness (1.3 ± 0.1 m). Some defects were observed on the coatings surface; however, the defects did not reach the AZ61 surface. Electrochemical tests performed in Hank's solution at 37 °C showed an improvement of corrosion resistance of AZ61 treated with fluoride conversion coatings when compared to the untreated material. Unconventionally prepared coating reached better electrochemical corrosion characteristics when compared to the conventionally prepared coating. Originality/value – Electrochemical corrosion characteristics of AZ61 magnesium alloy can be improved with fluoride conversion coatings. Two methods are used in the literature for the coatings preparation. The conventional method is based on dipping of the coated material to the HF and the unconventional method lies in dipping of the sample to the Na[BF4] salt melt. The main purpose of the present study is to analyze the conventionally and unconventionally prepared coatings in terms of chemical analysis, morphology and material corrosion protection (electrochemical corrosion characteristics), while the data are not provided in the literature according to the authors knowledge. Very similar coatings were prepared using both the methods from the morphological and chemical composition point of view. However, unconventionally prepared coating created in Na[BF4] salt melt reached better electrochemical corrosion characteristics compared to the coating prepared in HF.

Keywords

Magnesium alloy, Fluoride melt, Hydrofluoric acid, Conversion coating, Corrosion, Potentiodynamic curve, Hank's solution

Released

06.11.2017

Publisher

Emerald Publishing

Location

Spojené království Velké Británie a Severního Irska

Pages from

613

Pages to

619

Pages count

7

BibTex


@article{BUT140872,
  author="Juliána {Drábiková} and Stanislava {Fintová} and Jakub {Tkacz} and Pavel {Doležal} and Jaromír {Wasserbauer}",
  title="Unconventional fluoride conversion coating preparation and characterization",
  annote="Purpose – The purpose of this paper is to compare electrochemical corrosion characteristics of conventional and unconventional fluoride conversion coating prepared on magnesium alloy.
Design/methodology/approach – The chemical reaction of AZ61 with 38 wt. % hydrofluoric acid (HF) for 24 h was used as a conventional way of fluoride conversion coating preparation. The unconventionally prepared coating was created in Na[BF4] salt melt at 450 °C for 2 h. Morphology and chemical composition of prepared fluoride conversion coatings were studied with scanning electron microscopy and energy-dispersive X-ray spectroscopy. Electrochemical corrosion characteristics of the coatings were analyzed in Hank's solution using potentiodynamic tests.
Findings – Both the coating preparation ways resulted in a creation of uniform conversion coatings with the same thickness (1.3 ± 0.1 m). Some defects were observed on the coatings surface; however, the defects did not reach the AZ61 surface. Electrochemical tests performed in Hank's solution at 37 °C showed an improvement of corrosion resistance of AZ61 treated with fluoride conversion coatings when compared to the untreated material. Unconventionally prepared coating reached better electrochemical corrosion characteristics when compared to the conventionally prepared coating. 
Originality/value – Electrochemical corrosion characteristics of AZ61 magnesium alloy can be improved with fluoride conversion coatings. Two methods are used in the literature for the coatings preparation. The conventional method is based on dipping of the coated material to the HF and the unconventional method lies in dipping of the sample to the Na[BF4] salt melt. The main purpose of the present study is to analyze the conventionally and unconventionally prepared coatings in terms of chemical analysis, morphology and material corrosion protection (electrochemical corrosion characteristics), while the data are not provided in the literature according to the authors knowledge. Very similar coatings were prepared using both the methods from the morphological and chemical composition point of view. However, unconventionally prepared coating created in Na[BF4] salt melt reached better electrochemical corrosion characteristics compared to the coating prepared in HF.
",
  address="Emerald Publishing",
  chapter="140872",
  doi="10.1108/ACMM-02-2017-1757",
  howpublished="online",
  institution="Emerald Publishing",
  number="6",
  volume="64",
  year="2017",
  month="november",
  pages="613--619",
  publisher="Emerald Publishing",
  type="journal article in Web of Science"
}