Al-Mg Alloy Coating via Inert Gas Partitioned Thermal Spray
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Solution Overview
Problem
Conventional Al-Mg sprayed coatings on steel structures in marine environments suffer from high corrosion rates due to porosity, oxidation, and early local rust formation, leading to reduced durability and effectiveness in saltwater environments, necessitating frequent respraying and inadequate corrosion protection.
Innovation Solution
A thermal spraying method using a specialized gun that partitions the flame from the open air upstream and forcibly cools the material particles with a jet-gas or jet-mist downstream, preventing oxidation and achieving rapid cooling rates, resulting in a dense, non-porous coating with microstructures of 10 µm or less grain size, enhancing corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermal spraying is used to form Al-Mg alloy coating, then corrosion protection is provided through sacrificial anodic effect, but the coating becomes porous and allows salt penetration leading to high corrosion rates
Solution Approach 1:
The patent uses a double nozzle system where an inner nozzle delivers the Al-Mg alloy material and an outer nozzle supplies an inert gas (such as nitrogen or argon) to create a protective atmosphere around the material stream. This inert atmosphere prevents oxidation of the magnesium during spraying and reduces porosity in the resulting coating, thereby improving corrosion resistance while maintaining the sacrificial anodic protection mechanism.
2Quantity of substance
If ordinary flame spray gun is used, then Al-Mg alloy coating is formed, but magnesium readily oxidizes in flame reducing magnesium concentration and corrosion protection
Solution Approach 1:
The patent employs a double nozzle configuration where the outer nozzle delivers inert gas to surround the Al-Mg alloy material as it travels from the inner nozzle to the substrate. This creates a controlled inert atmosphere that prevents magnesium oxidation during the spraying process, preserving the magnesium concentration in the coating and maintaining its corrosion protection capabilities.
Solution Approach 2:
The inert gas acts as an intermediary substance between the Al-Mg alloy material and the ambient air. It forms a protective barrier that mediates the interaction between magnesium and oxygen, preventing direct contact and oxidation while allowing the material to be deposited on the substrate. This intermediary approach successfully preserves magnesium concentration without requiring post-spray vacuum or other complex measures.
3Duration of action of stationary object
If conventional spraying is used, then coating is formed with large grain size of several tens of μm, but corrosion develops from grain boundaries reducing durability
Solution Approach 1:
The patent uses an inert gas atmosphere during spraying to control the solidification process of the Al-Mg alloy particles. This inert environment prevents oxidation that would normally occur at grain boundaries during conventional spraying, allowing for the formation of a finer grain structure with size of 10 μm or less. The reduced grain size eliminates corrosion pathways along grain boundaries, significantly improving coating durability in marine environments.
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 method produces a corrosion-resistant Al-Mg alloy coating with improved durability, reduced porosity, and enhanced scratch resistance, effectively preventing seawater penetration and extending the lifespan of steel structures in aggressive saltwater environments beyond conventional standards.
Implementation Method 1
a flame including melted material particles is jetted toward a substrate
Implementation Method 2
thermal spraying method using a specialized gun
Implementation Method 3
the material particles and the flame are forcibly cooled by a jet-gas or jet-mist before reaching the substrate
Implementation Method 4
in a downstream region (the area continuing to the front of the upstream region), the material particles and the flame are forcibly cooled by a jet-gas or jet-mist
Implementation Method 5
the flame is partitioned from the open air in an upstream region on said jet path (which is to say the region in which the material particles are melted)
Data Source
Figure 1~2
Figure 3
Figure 4~5(d)
AI summary
[Problem] To provide a corrosion-resistant coating that exhibits greater corrosion protection in saltwater environments and the like than was conventional, a method for forming the same, and a device for forming the same. [Solution] A corrosion-resistant alloy coating is formed on a substrate surface by: a) using a thermal spray gun, having a function wherein a flame including melted material particles is jetted toward a substrate, and the flame is partitioned from the open air in an upstream region on said jet path (which is to say the region in which the material particles are melted), and a function wherein, in a downstream region (the area continuing from the upstream region), the material particles and the flame are forcibly cooled by a jet-gas or jet-mist before reaching the substrate; and b) using a corrosion-resistant alloy material comprising aluminum, for the material particles.