Zn-Al-Mg-Si Plated Steel for Corrosion and Luster Stability
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Solution Overview
Problem
Existing Zn-based plated steel materials face issues with maintaining metallic luster and appearance over a long time due to weak sacrificial corrosion resistance and susceptibility to corrosion, particularly in outdoor environments.
Innovation Solution
A Zn-Al-Mg-based plated steel material with a specific composition and structure, including a Zn-Al-Mg alloy layer and an Al-Fe alloy layer, forms a dense oxide film on the surface, enhancing corrosion resistance and maintaining appearance by controlling the precipitation of Mg2Si and promoting an Al-Si-O-based intermetallic compound formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Zn-based plated steel sheets are used to provide strong sacrificial corrosion-preventive action, then corrosion resistance is improved, but metallic luster and appearance are likely to change over time due to white rust and discoloration
Solution Approach 1:
The invention changes the chemical composition parameters of the plating layer by adding specific amounts of Al (1-10 mass%), Si (0.03-3 mass%), and other elements to the Zn-based plating. This compositional modification enables the formation of a dense oxide film that provides both corrosion protection and appearance stability, resolving the contradiction between sacrificial corrosion action and metallic luster maintenance.
Solution Approach 2:
The invention creates a composite plating layer structure consisting of Zn as the base metal with Al-Si-O-based intermetallic compounds and dense oxide films formed on the surface. This composite structure combines the sacrificial corrosion protection of Zn with the appearance stability of the Al-Si-O oxide film, simultaneously achieving both corrosion resistance and appearance maintenance.
2Stability of the object's composition
If Al-based plated steel sheets are used to maintain appearance and metallic luster, then appearance stability is improved, but sacrificial corrosion-preventive action becomes weak
Solution Approach 1:
The invention modifies the plating composition by using Zn as the primary base metal (90-99 mass%) rather than Al, but adds controlled amounts of Al (1-10 mass%) and Si (0.03-3 mass%) to enable oxide film formation. This parameter change maintains strong sacrificial corrosion protection from the Zn base while achieving appearance stability through the formed oxide film.
Solution Approach 2:
The Al-Si-O-based intermetallic compounds and dense oxide film act as an intermediary layer on the Zn-based plating surface. This intermediary layer provides the appearance stability and metallic luster characteristic of Al-based plating, while the underlying Zn base metal maintains strong sacrificial corrosion protection.
3Stability of the object's composition
If coating treatment is applied to Zn plated steel sheet to maintain appearance, then appearance stability is improved, but cost increases and metallic luster is lost
Solution Approach 1:
The invention enables the Zn-based plating to self-form a dense oxide film with Al-Si-O-based intermetallic compounds through controlled composition and heat treatment. This self-service mechanism eliminates the need for additional coating treatments, maintaining metallic luster while reducing manufacturing costs and process complexity.
Solution Approach 2:
The invention changes the plating composition parameters to include Al (1-10 mass%) and Si (0.03-3 mass%), which enable spontaneous oxide film formation. This parameter modification allows the material to inherently maintain appearance stability without requiring additional coating processes, thereby reducing manufacturing cost and preserving metallic luster.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a Zn-based plated steel material with high corrosion resistance and minimal change in appearance over time, maintaining metallic luster even in outdoor conditions by forming a dense oxide film that prevents corrosion and blackening.
Implementation Method 1
an Al-Si-O-based intermetallic compound is contained in the plating layer... forms a dense oxide film on the surface
Implementation Method 2
controlling the precipitation of Mg2Si and promoting an Al-Si-O-based intermetallic compound formation
Data Source
Figure 1
AI summary
A plated steel material having a plating layer having an average chemical composition containing, in mass%, Zn: more than 50.00%, Al: more than 15.0% and less than 30.0%, Mg: more than 5.0% and less than 15.0%, and Si: 0.25% or more and less than 3.50%, and impurities, and wherein a total amount (ΣA) of at least one selected from the group consisting of Sn, Bi and In is less than 1.00%, a total amount (ΣB) of at least one selected from the group consisting of Ca, Y, La, Ce and Sr is 0.02% or more and less than 0.60%, 0.02%ormoreandlessthan0.60%,2.0≤Mg/Si<20.0Formula1, 3.0≤Si/ΣB<24.0 and 26.0≤Si/ΣB×Mg/Si<375.0 are satisfied, and in an X-ray diffraction pattern of the surface of the plating layer, a diffraction intensity ratio R1 defined by R1={I(16.18°)+I(32.69°)}/I(27.0°) (Formula 4) satisfies 2.5<R1 (Formula 5) is used.