Conversion coating

A Conversion coating is a chemical or electro-chemical treatment applied to manufactured parts that superficially converts the material into a thin adhering coating of an insoluble compound. These coatings are commonly applied to protect the part against corrosion, to improve the adherence of other coatings, for lubrication or for decoration. ^[1]^[2]^[3]^[4]

Types[]

The most common conversion coating processes for metal parts with industrial use include

Chromate (aluminum, steel)
Phosphate (steel)
Bluing (steel)
Blackening (steel)
Anodizing (aluminum)
(magnesium)^[5]
(zinc, zinc-nickel)^[6]^[7]
(steel, aluminum, magnesium, galvanized steel).^[1]^[8]^[9]
(steel, aluminum, magnesium).^[1]
(aluminum, magnesium, titanium)^[10]^[11]

Non-metallic substrates[]

Conversion coatings have been studied for non-metallic substrates, such as for protection of fluorozirconate glasses used in optoelectronics.^[12]

Regulations[]

US military specifications for conversion coatings include MIL-DTL-81706 and MIL-DTL-5574.

References[]

^ ^a ^b ^c I. Milošev and G. S. Frankel (2018): "Review—Conversion Coatings Based on Zirconium and/or Titanium". Journal of the Electrochemical Society, volume 165, issue 3,pages C127-C144. doi:10.1149/2.0371803jes
^ "[1]"
^ "[2]"
^ "Fastener Surface Conversion", In: FastenerData.co.uk
^ M. A. Gonzalez-Nunez, C. A. Nunez-Lopez, P. Skeldon, G. E. Thompson, H. Karimzadeh, P. Lyon, and T.E.Wilks (1995): "A non-chromate conversion coating for magnesium alloys and magnesium-based metal matrix composites". Corrosion Science, volume 37, issue 11, pages 1763-1772. doi:10.1016/0010-938X(95)00078-X
^ A. A. O. Magalhães, I. C. P. Margarita, O. R. Mattos (2004): "Molybdate conversion coatings on zinc surfaces". Journal of Electroanalytical Chemistry, volume 572, issue 2, pages 433-440. doi:10.1016/j.jelechem.2004.07.016
^ J. A. Wharton, G. D. Wilcox, and K. R Baldwin (1996): "Non-Chromate Conversion Coating Treatments For Electrodeposited Zinc-Nickel Alloys". Transactions of the IMF - The International Journal of Surface Engineering and Coatings, volume 74, issue 6, pages 210-213. doi:10.1080/00202967.1996.11871128
^ Charles E. Tomlinson (1998): "Chromate-free conversion coatings for metals". US Patent 5759244, filed on 1996-10-09, granted on 1998-06-02, expired on 2016-10-09.
^ Raoling Wang (2018): "Chromium-free aluminum conversion coating agent, aluminum material, and surface conversion coating treatment method". Patent WO2018006270, filed on 2016-07-05, granted on 2018-01-11.
^ Lishi Wang, Tao Feng, Shanwen Yu, Yihang Cheng, Zhixiang Bu and Xinbin Hu (2020): "Fluoride effect on plasma electrolytic oxidation coating formed on Mg-Al alloy in alkaline electrolytes". Materials Research Express, volume 7, issue 1, article 016412. doi:10.1088/2053-1591/ab60a7
^ Liu Feng, Shan Dayong, Song Yingwei, Liu Xianbin, and Han Enhou (2012): "Highly corrosion-resistant ceramic coating solution prepared through magnesium alloy surface micro-arc oxidation and application thereof". Chinese patent 101994145, filed on 2009-08-19, granted on 2012-05-23.
^ A. P. Rizzato, C. V. Santilli, S. H. Pulcinelli, Y. Messaddeq, and P. Hammer (2004): "XPS Study of the Corrosion Protection of Fluorozirconate Glasses Dip-Coated with SnO2 Transparent Thin Films". Journal of Sol-Gel Science and Technology, volume 32, pages 155–160. doi:10.1007/s10971-004-5781-9

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[milo2018-1] I. Milošev and G. S. Frankel (2018): "Review—Conversion Coatings Based on Zirconium and/or Titanium". Journal of the Electrochemical Society, volume 165, issue 3,pages C127-C144. doi:10.1149/2.0371803jes

[rit-2] "[1]"

[mate-3] "[2]"

[fast-4] "Fastener Surface Conversion", In: FastenerData.co.uk

[gonz1995-5] M. A. Gonzalez-Nunez, C. A. Nunez-Lopez, P. Skeldon, G. E. Thompson, H. Karimzadeh, P. Lyon, and T.E.Wilks (1995): "A non-chromate conversion coating for magnesium alloys and magnesium-based metal matrix composites". Corrosion Science, volume 37, issue 11, pages 1763-1772. doi:10.1016/0010-938X(95)00078-X

[maga2004-6] A. A. O. Magalhães, I. C. P. Margarita, O. R. Mattos (2004): "Molybdate conversion coatings on zinc surfaces". Journal of Electroanalytical Chemistry, volume 572, issue 2, pages 433-440. doi:10.1016/j.jelechem.2004.07.016

[whar1996-7] J. A. Wharton, G. D. Wilcox, and K. R Baldwin (1996): "Non-Chromate Conversion Coating Treatments For Electrodeposited Zinc-Nickel Alloys". Transactions of the IMF - The International Journal of Surface Engineering and Coatings, volume 74, issue 6, pages 210-213. doi:10.1080/00202967.1996.11871128

[tom1998-8] Charles E. Tomlinson (1998): "Chromate-free conversion coatings for metals". US Patent 5759244, filed on 1996-10-09, granted on 1998-06-02, expired on 2016-10-09.

[wang2018-9] Raoling Wang (2018): "Chromium-free aluminum conversion coating agent, aluminum material, and surface conversion coating treatment method". Patent WO2018006270, filed on 2016-07-05, granted on 2018-01-11.

[wang2020-10] Lishi Wang, Tao Feng, Shanwen Yu, Yihang Cheng, Zhixiang Bu and Xinbin Hu (2020): "Fluoride effect on plasma electrolytic oxidation coating formed on Mg-Al alloy in alkaline electrolytes". Materials Research Express, volume 7, issue 1, article 016412. doi:10.1088/2053-1591/ab60a7

[feng2012-11] Liu Feng, Shan Dayong, Song Yingwei, Liu Xianbin, and Han Enhou (2012): "Highly corrosion-resistant ceramic coating solution prepared through magnesium alloy surface micro-arc oxidation and application thereof". Chinese patent 101994145, filed on 2009-08-19, granted on 2012-05-23.

[rizz2004-12] A. P. Rizzato, C. V. Santilli, S. H. Pulcinelli, Y. Messaddeq, and P. Hammer (2004): "XPS Study of the Corrosion Protection of Fluorozirconate Glasses Dip-Coated with SnO2 Transparent Thin Films". Journal of Sol-Gel Science and Technology, volume 32, pages 155–160. doi:10.1007/s10971-004-5781-9

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