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

Abstract

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.

Study of the role of aluminium and corrosion mechanism in galvalume coating in the marine atmospheric environment

“…Galvalume coatings exhibit unique dual-phase dendritic crystallisation that combines the surface protection and high durability of Al with the electrochemical protection properties of Zn (Moreira et al , 2006; Jiang et al , 2014). Typically, it is two to four times more durable and resistant to corrosion under atmospheric conditions than galvanised coatings (Vishwanatha and Panda, 2022; Hoang et al , 2022; Morcillo et al , 1994; Yasakau, et al , 2016). Galvalume coatings have several applications such as household appliances and automobile exhaust systems (Guo, et al , 2018; Jarwali and Nakamura, 2016).…”

Physical and Chemical Properties of High-Temperature Silicone-Based Polymer Coatings Applied on Different Surface Roughnesses

“…Previous studies on silicone-based coatings included the type of silicone resin for the long-term heat resistance of the coating [3], adhesion properties, variety of precursors and polymer-to-ceramic conversion of silicone-based coatings [20], chemical properties of silane-based coatings [21], flake ZnAl alloy as an effective pigment in silicate coatings for the corrosion protection of steel [22], and the interface properties between water-based inorganic zinc silicate coating modified by organosilicon and iron substrate [11].…”

Effect of Aluminum Flakes on Corrosion Protection Behavior of Water-Based Hybrid Zinc-Rich Coatings for Carbon Steel Substrate in NaCl Environment

“…Aluminum lamellae present several advantages, because aluminum has a very low potential when in metallic form and is very stable when an Al 2 O 3 layer is formed on the surface. This stability in aqueous medium is a great advantage in water-based coatings during batch production and can be achieved with zinc, by making flakes of Zn-Al alloys, which provide good performance [35]. Aluminum lamellae are also aesthetically interesting, as they allow the formulation of a silver-gray color with a metallic effect due to the light reflecting on the surface of the flakes [36], which is of interest in the automobile industry.…”