Silicate Glass-like Coating for Metal Oxidation Resistance
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Solution Overview
Problem
Current protective coatings for metals like titanium and stainless steel are inadequate in providing high temperature oxidation resistance, corrosion resistance, and stability across various pH levels, as well as resistance to accelerated corrosion testing and fogging.
Innovation Solution
A method involving the formation of an oxide layer on metal substrates followed by the application of a silicate glass-like layer composed of silicon, oxygen, sodium, and optionally lithium and boron, using a process that includes pickling, chemical passivation, and curing at elevated temperatures or with infrared exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If natural oxide layers are allowed to develop over time without controlled parameters, then the coating forms passively, but the surface structure becomes rough, irregular, and non-continuous
Solution Approach 1:
The patent applies preliminary mechanical treatment (abrasive blasting) to remove naturally existing oxide layers before controlled passivation. This preliminary action prevents the formation of rough, irregular oxide structures by eliminating them before the controlled oxide layer forms, ensuring a uniform surface structure from the outset.
Solution Approach 2:
The patent controls the passivation process under specific parameters (controlled environment, specific duration, controlled oxide thickness) to transform the uncontrolled natural oxidation process into a controlled one. This parameter control ensures the oxide layer forms with uniform thickness and continuous structure rather than rough and irregular morphology.
2Reliability
If conventional protective coatings are applied to metal surfaces, then corrosion resistance is provided, but resistance to high temperature oxidation and stability across pH levels remain inadequate
Solution Approach 1:
The patent creates a composite protective system consisting of a controlled oxide layer (titanium dioxide or chromium oxide) formed through controlled passivation, combined with a silicate glass-like coating applied over it. This composite structure provides both corrosion resistance from the oxide layer and enhanced high-temperature oxidation resistance and pH stability from the silicate glass-like coating, solving the limitations of conventional single-layer coatings.
3Reliability
If anodisation is used to increase oxide layer thickness, then protective properties are improved, but the process complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the complex anodisation process from the treatment sequence, replacing it with a simpler controlled chemical passivation process. By removing the electrochemical anodisation step and using only controlled chemical passivation followed by silicate coating, the patent achieves adequate protective oxide layer thickness without the equipment complexity and process intricacy of anodisation.
4Temperature
If passive metal surfaces are exposed to high temperatures, then oxidation resistance is tested, but surface colour changes occur which are usually not desired
Solution Approach 1:
The patent uses a composite structure where the silicate glass-like coating is applied over the oxide layer. This outer silicate layer acts as a protective barrier that prevents direct oxidation of the metal substrate at high temperatures and maintains surface appearance stability, while allowing the underlying oxide layer to provide corrosion resistance. The silicate coating prevents the colour changes that would otherwise occur in the metal oxide at high temperatures.
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 resulting coated metal products exhibit enhanced durability, resistance to high temperature oxidation, corrosion, and environmental factors, while maintaining a natural appearance and adhering well to secondary coatings.
Implementation Method 1
curing the applied coating on the oxide layer to provide a silicate coating layer by: a) heating the coated, passive layer to a temperature of at least 200 °C
Implementation Method 2
b) exposing the coated, passive layer to an infrared source
Implementation Method 3
forming an oxide layer on the metal surface by means of a chemical or electrochemical process
Implementation Method 4
The process of formation of an oxide layer on titanium/titanium alloys and stainless steel is a well-known and widely used industrial procedure to produce protective and/or decorative coatings
Implementation Method 5
Anodisation is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of the metal
Data Source
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AI summary
The present invention relates to metals or metal alloys comprising a protective silicate glass-like coating, and methods for coating the metals or metal alloys. The methods comprise removal of any existing oxide layer from the metal or metal alloy, formation of a new oxide layer on the metal or metal alloy using chemical passivation or exposure to a gaseous oxidising environment, coating the oxidised metal or metal alloy with an aqueous silicate solution, and curing the coating.