Zn-Al-Mg Hot-Dip Coating Composition for Luster and Corrosion Resistance
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Solution Overview
Problem
Zn—Al—Mg-based hot-dip plated steel sheets lack sufficient metallic luster and corrosion resistance, as they often exhibit a satin-like appearance due to varying phases and microstructures that affect their surface finish.
Innovation Solution
Adjust the chemical composition of the hot-dip plated layer to include Al: 10 to 22 mass % and Mg: 1.0 to 10 mass %, with controlled area fractions of the [Zn phase] less than 20% and specific ratios of [Zn phase] to [Al/MgZn2/Zn ternary eutectic structure] to enhance metallic luster and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If various phases and microstructures are present in a mixed state in the hot-dip plated layer, then corrosion resistance is improved, but the surface external appearance becomes satin-like with reduced metallic luster
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters (Al: 10-22 mass%, Mg: 1.0-10 mass%) and microstructural parameters (area fraction of Zn phase < 20%) to transform the plating layer from a multi-phase mixed state to a dominant Al phase state, thereby achieving both excellent corrosion resistance and superior metallic luster
Solution Approach 2:
The patent applies local quality by creating a specific microstructural distribution where the Al phase occupies the majority area fraction, while controlling the presence of other phases (Zn phase < 20%, Al/MgZn2/Zn ternary eutectic structure) to achieve localized optical properties that enhance metallic luster while maintaining corrosion resistance
2Reliability
If Al and Mg are incorporated into the hot-dip galvanized layer to improve corrosion resistance, then corrosion resistance is enhanced, but the surface external appearance becomes satin-like
Solution Approach 1:
The patent applies parameter changes by optimizing the Al content (10-22 mass%) and Mg content (1.0-10 mass%) within specific ranges, and controlling the area fraction of Zn phase to less than 20%, to achieve a plating layer that simultaneously exhibits enhanced corrosion resistance and improved surface external appearance with metallic luster
Solution Approach 2:
The patent applies composite materials by creating a controlled multi-phase composite structure in the hot-dip plated layer, where the Al phase forms the dominant matrix with controlled amounts of other phases, achieving a composite material that combines both protective corrosion resistance and desirable metallic luster appearance
Data Source
AI summary
A Zn—Al—Mg-based hot-dip plated steel sheet includes a steel sheet and a hot-dip plated layer formed on a surface of the steel sheet, in which the hot-dip plated layer contains, as an average composition, Al: more than 10 to 22 mass % and Mg: 1.0 to 10 mass %, with a remainder including Zn and impurities, and in a case where a 5 mm square cross section parallel to a surface of the hot-dip plated layer is exposed at any position of a 3t/4 position, a t/2 position, and a t/4 position from the surface with a thickness of the hot-dip plated layer represented by t, an area fraction of a [Zn phase] of a plating microstructure in at least one of the cross sections is less than 20%.