Flake ZnAl Alloy as an Effective Pigment in Silicate Coatings for the Corrosion Protection of Steel

• Published in: Coatings (Basel) Vol. 12; no. 8; p. 1046
• Main Authors: Hoang, Nguyen, Khoa, Truong Anh, Nhung, Le Thi, Phuong, Phan Minh, Binh, Tran Dinh, Hang, To Thi Xuan, Chi, Nguyen Van, Nguyen, Thanh-Danh
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.08.2022
• Subjects: Alloys; Carbon steel; Carbon steels; Cathodic protection; Chemical properties; Coating processes; Corrosion; Corrosion potential; Corrosion prevention; Corrosion products; Corrosion resistance; Corrosion resistant steels; Electrochemical analysis; Electrochemical impedance spectroscopy; Electrodes; Electrolytes; Flakes; Investigations; Mechanical properties; Metals; Methods; Morphology; Pigments; Potassium; Protective coatings; Pull off tests; Salt spray tests; Silica; Spectrum analysis; Steel; Substrates; VOCs; Volatile organic compounds; Zinc; Zinc alloys; Zinc base alloys; Vietnam; New York; United States > US; China
• ISSN: 2079-6412; 2079-6412
• DOI: 10.3390/coatings12081046

Spherical zinc is well known as an effective pigment for the corrosion protection of carbon steel. However, a high proportion of spherical Zn in a coating leads to difficulties in fabricating the coating solution and increased cost. In this work, the influence of flake ZnAl alloy in silicate coatings on the corrosion protection properties of steel substrates was investigated. The electrochemical behaviour of coatings containing different flake ZnAl alloy content immersed in NaCl solution (3.5 wt%) was evaluated using an electrochemical impedance spectroscopy (EIS) method. A salt spray test was performed to evaluate corrosion on the coating surface. Pull-off tests of the coatings before and after the salt spray process were performed, and the surface morphology was analysed to determine the degradation of corrosion resistance. The results show that silicate coating containing flake ZnAl alloy (25 wt%) possesses the highest total resistance (1417 Ω) and the longest time to the appearance of white rust (720 h). The surface morphology of the coating containing 25 wt% flake ZnAl alloy was found to include corrosion products with the most compacted surface, which effectively prevents the penetration of electrolytes to the interface between the coating and the steel.