Magnesium-Lithium Alloy Corrosion Resistance via Fluorinated Coating
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Solution Overview
Problem
Conventional magnesium-lithium alloys have insufficient corrosion resistance due to the inability to form a coating film with a large amount of fluorine, leading to poor performance in high-temperature and high-humidity environments.
Innovation Solution
A magnesium-lithium alloy member with a substrate comprising at least 90% magnesium and lithium, coated with a film containing more than 50% fluorine and less than 5% oxygen, formed through an anodization process using a neutral ammonium fluoride solution, which suppresses hydrogen gas generation and enhances corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional fluorination methods (dip treatment with acidic ammonium fluoride or conversion treatment with hydrogen fluoride) are used on magnesium-lithium alloy, then the surface is treated, but the fluorine content in the coating film remains insufficient
Solution Approach 1:
The patent changes the chemical parameters of the treatment liquid from acidic to neutral pH, and adjusts the composition to contain ammonium fluoride and aluminum fluoride. This parameter change enables the formation of a coating film with fluorine content of 40-80 atom%, significantly higher than conventional methods, thereby resolving the contradiction between fluorine content and corrosion resistance
Solution Approach 2:
The patent creates a composite coating film containing multiple elements (Mg, Li, Al, F, O) with specific compositional ratios. The coating film is a composite material formed by the reaction of the magnesium-lithium alloy substrate with the neutral ammonium fluoride treatment liquid, achieving both high fluorine content and excellent corrosion resistance through the synergistic effect of multiple elements
2Weight of moving object
If magnesium-lithium alloy is used to reduce weight, then weight saving is achieved, but corrosion resistance deteriorates in high-temperature and high-humidity environments
Solution Approach 1:
The patent applies preliminary surface treatment by immersing the magnesium-lithium alloy in neutral ammonium fluoride treatment liquid before the alloy is exposed to corrosive environments. This preliminary fluorination treatment forms a protective coating film that prevents subsequent corrosion, allowing the alloy to maintain both its light weight and corrosion resistance in service
Solution Approach 2:
The patent creates an inert protective environment on the alloy surface by forming a fluorinated coating film that is chemically stable and resistant to corrosion. This inert coating layer isolates the reactive magnesium-lithium alloy from the corrosive external environment, particularly in high-temperature and high-humidity conditions
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 effectively inhibits corrosion by forming a stable fluorinated coating with a high fluorine content, significantly improving the alloy's durability in harsh environments and preventing film swelling or peeling.
Implementation Method 1
a method for manufacturing an alloy member... applying a voltage between the anode and the cathode to dispose a coating film on the substrates
Implementation Method 2
disposing a cathode substrate and the substrate made of magnesium-lithium alloy as an anode in an aqueous solution of neutral ammonium fluoride; and applying a voltage between the anode and the cathode
Data Source
AI summary
Provided is an alloy member including a substrate made of magnesium-lithium alloy with a sum of content of magnesium and content of lithium of 90 mass % or more and a coating film disposed on the substrate. The coating film contains fluorine and oxygen, with a fluorine content of more than 50 atom % and an oxygen content of less than 5 atom %.