Evaluation of the Growth Mechanism of Ti-Containing Conversion Coatings Using XPS

Abstract:

Ti-containing coatings as chromate replacement were prepared on electrogalvanized steel. Zinc coatings were deposited from a weak acid chloride bath. Cr-free conversion coatings were deposited from bath composed of: TiCl₃, H₂SiF₆, H₂O₂ and oxalic acid. XPS was used to evaluate chemical composition of the coatings as a function of deposition time. Deposited coating were of conversion type. Regardless of the achieved conversion coating thickness, Zn from the substrate was always present. In the coatings were identified: Zn₂SiO₄ / Zn₄Si₂O₇(OH)₂, ZnTiO₃, ZnO, Zn (OH)₂, Zn⁰, SiOx and Ti-O-Si in varying proportions. The chemical composition of the outer surface of the coating depended on deposition time, e.g. in a time interval 0-300 s 30 fold increase of the Si:Ti ratio and 20 fold of the Si:Zn ratio were observed. Estimated thickness of conversion coating was 3, 14, 35, and 100 nm for the time deposition of 1, 40, 80 and 300 s respectively. It is the proposed model for distinguishing Zn (0) phase from Zn (2+) quantitatively, based on the Zn L₃M₄₅M₄₅ spectrum. The composition of the ZnTiSi conversion coating determined its mechanical properties and corrosion resistance. Standard tests carried out showed that the coatings obtained at the time of 20-40 s had the best corrosion performance and mechanical resistance

• Periodical: Solid State Phenomena (Volume 227)
• Pages: 159-162
• DOI: https://doi.org/10.4028/www.scientific.net/SSP.227.159
• Online since: January 2015
• Authors: Wlodzimierz Tylus*, Juliusz Winiarski, Bogdan Szczygieł
• Keywords: Conversion Coating, XPS, Zinc Coating

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