A comparative study of eco-friendly hybrid thin films: With and without organic coating application

• Published in: Progress in organic coatings Vol. 125; pp. 432 - 442
• Main Authors: Eivaz Mohammadloo, H., Sarabi, A.A., Asemani, H.R., Ahmadi, P.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.12.2018; Elsevier BV
• Subjects: Adhesion; Adhesion tests; Adhesive strength; Chromate coatings; Coated electrodes; Coating effects; Comparative studies; Conversion coating; Conversion coatings; Corrosion; Corrosion prevention; EIS; Micro-electrode; Microelectrodes; Nickel; Organic coatings; Phytic acid; Protective coatings; Salt spray tests; Substrates; Surface properties; Thin films; Ti-based conversion coating; Titanium; Tungsten; Micro-electrode; Corrosion; Adhesion; EIS; Ti-based conversion coating
• ISSN: 0300-9440; 1873-331X
• DOI: 10.1016/j.porgcoat.2018.09.023

[Display omitted] •Five types of Ti-based conversion coatings were applied on steel substrates.•Tungsten micro-electrode was used for study the Ti conversion coating formation.•Local pH increase at interface facilitates the precipitation of Ti compounds.•TiNiCC could be regarded as replacement for conventional conversion coatings. Effect of various eco-friendly surface treatments based on Titanium conversion coatings (in the presence of molybdenum, nickel, phytic and hexaflourozirconic acid compounds) on electrochemical and surface properties of steel substrates was studied comprehensively. Moreover, chromate and tri-cationic phosphate conversion coatings were used as references. Tungsten micro-electrode was used to study the film formation mechanism of conversion coatings and obtained results indicated that an increase in local pH (about 4 units) is responsible for the precipitation of coatings. FE-SEM and AFM images revealed that modification by Ni ions results in formation of uniform and pack layer structure which improves barrier properties of conversion coating. Moreover, the interaction of conversion coatings with epoxy coating was evaluated with respect to anti-corrosion and adhesion performance. Obtained results indicated that Ti-based surface treatments modified by nickel ions and phytic acid, have better adhesion strength to epoxy coating (4.2 and 4 MPa respectively) and indicated better anti-corrosion performance (according to EIS and salt-spray tests) compared to traditional chromate and phosphate conversion coatings.