Experimental study on corrosion resistance of Zn–Al–Mg alloy coating of high-strength steel wires for bridge cables

Abstract

Purpose This paper aims to figure out the conundrum that the corrosion resistance longevity of steel wires for bridge cables was arduous to meet the requirements. Design/methodology/approach The “two-step” hot-dip coating process for cable steel wires was developed, which involved first hot-dip galvanizing and then hot-dip galvanizing of aluminum magnesium alloy. The corrosion rate, polarization curve and impedance of Zn–6Al–1Mg and Zn–10Al–3Mg alloy-coated steel wires were compared through acetate spray test and electrochemical test, and the corrosion mechanism of Zn–Al–Mg alloy-coated steel wires was revealed. Findings The corrosion resistance of Zn–10Al–3Mg alloy-coated steel wires had the best corrosion resistance, which was more than seven times that of pure zinc-coated steel wires. The corrosion current of Zn–10Al–3Mg alloy-coated steel wires was lower than that of Zn–6Al–1Mg alloy-coated steel wires, whereas the capacitive arc and impedance value of the former were higher than that of the latter, making it clear that the corrosion resistance of Zn–10Al–3Mg was better than that of Zn–6Al–1Mg alloy coating. Moreover, the Zn–Al–Mg alloy-coated steel wires for bridge cables had the function of coating “self-repairing.” Originality/value Controlling the temperature and time of the hot dip galvanizing stage can reduce the thickness of transition layer and solve the problem of easy cracking of the transition layer in the Zn–Al–Mg alloy coating due to the Sandelin effect.

A review of physical properties of hot-dip galvanized coating layer by layer and their respective electrochemical corrosion behavior

“…Batch hot-dip galvanizing will form a protective coating structure in the temperature range of 440°C -480°C. Figure 2 shows the growth diagram of the Fe-Zn alloy layer (Hu et al, 2023;Bai and Wu, 2002). At t 0 , the steel matrix contacts the molten zinc pool, and the Fe on the surface of the matrix dissolves rapidly in the zinc pool.…”

“…The sublayers assume a crucial role in the coating formation process, exhibiting distinct physical properties and electrochemical corrosion behaviors. Therefore, it is worth studying the corrosion behavior of these sublayers to further understand the corrosion resistance mechanism of the hot-dip galvanized coating (Hu et al, 2023;Hu et al, 2023;Bai and Wu, 2002;Li et al, 2022aLi et al, , 2022bLi et al, , 2022cLi et al, ,,2022d).…”

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

“…Experiments have been conducted to compare the performance of Al-Zn coatings with different processes (dos Santos et al , 2015; Edavan and Kopinski, 2009; Alvarenga and Lins, 2016). The corrosion resistance of three-component alloy coatings has also been investigated (Lee et al , 2019; Hu et al , 2023). Zhang et al (2018) demonstrated that the behaviour of the galvalume was similar as a bare Al sheet.…”

Roles of Al and Mg on the Microstructure and Corrosion Resistance of Zn-Al-Mg Hot-Dipped Coated Steel

“…Previous studies have indicated that the addition of Mg and Al elements to the molten bath undergoes eutectic reactions, resulting in the generation of various alloy phases such as MgZn 2 , which may form the Zn/MgZn 2 binary eutectic phase or Zn/Al/MgZn 2 ternary eutectic phase. These alloy phases, or the eutectic phase of zinc, exhibit preferential corrosion, reducing the dissolution rate of zinc, and thereby improving the corrosion resistance of the coating [4,[15][16][17]. The amount of Mg and Al added into the molten bath also affects the structure and corrosion resistance.…”