Thermoset-Coated Fasteners for Galvanic Corrosion Isolation
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Solution Overview
Problem
Galvanic corrosion occurs when dissimilar metals with different anodic indices are in contact in the presence of an electrolyte, leading to accelerated corrosion and potential structural integrity issues, particularly in the automotive and aerospace industries, where lightweight materials are used but cannot be applied to fasteners due to cost and mechanical property concerns.
Innovation Solution
A two-article system with at least one component coated with a thermoset coating, comprising an epoxy resin and curing agents, which cures rapidly at high temperatures and forms a cross-linked barrier to prevent galvanic corrosion, while maintaining mechanical properties and resistance to temperature fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If lightweight materials (aluminum, magnesium, carbon fiber) are used for fasteners, then weight reduction is achieved, but mechanical strength and corrosion resistance deteriorate
Solution Approach 1:
The patent applies composite materials by combining steel fasteners with a thermoset coating layer. The steel substrate provides the required mechanical strength while the thermoset coating provides corrosion resistance and enables compatibility with lightweight structures. This composite approach allows the fastener system to meet both strength requirements and weight reduction goals.
2Adaptability or versatility
If dissimilar metals with different anodic indices are used, then material selection flexibility is improved, but galvanic corrosion resistance deteriorates
Solution Approach 1:
The thermoset coating acts as an intermediary barrier between dissimilar metals. It electrically isolates the fastener from contact with the lightweight structure (aluminum, magnesium, or carbon fiber), preventing galvanic current flow. This allows designers to freely select from various material combinations without concern for galvanic corrosion, as the coating mediates the interaction between dissimilar metals.
3Reliability
If polymeric coatings (nylon) are applied to prevent galvanic corrosion, then corrosion resistance is improved, but mechanical properties and engagement reliability deteriorate
Solution Approach 1:
The patent changes the material parameter from soft polymeric coatings to thermoset coatings with higher mechanical strength and lower elasticity. The thermoset coating maintains adequate thickness for corrosion protection while being thin enough to allow proper bolt engagement. Its low elasticity prevents tension loss during thermal cycling, maintaining engagement reliability.
4Reliability
If coating thickness is increased to improve corrosion protection, then galvanic corrosion resistance is improved, but coating resiliency and tension maintenance deteriorate
Solution Approach 1:
The patent changes the material parameter from elastic polymers to low-elasticity thermoset materials. This allows the coating to be sufficiently thin (maintaining resiliency) while still providing adequate corrosion protection. The low elasticity ensures the coating maintains its thickness and protective capability during thermal expansion and contraction, preventing tension loss.
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 thermoset coating significantly reduces galvanic corrosion, as evidenced by less than 3% pitting after 15 years in simulated tests, while maintaining bolt tension and mechanical integrity, and can withstand elevated temperatures without adverse effects.
Implementation Method 1
comprising an epoxy resin and curing agents, which cures rapidly at high temperatures and forms a cross-linked barrier to prevent galvanic corrosion
Implementation Method 2
can withstand elevated temperatures without adverse effects
Data Source
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AI summary
A method to prevent corrosion of a susceptible article of a two-article system, in which first and second articles of the two-article system have surfaces facing one another and in which the two articles have different anodic indices includes applying a coating material to the surface of the first article and curing the coating material on the surface of the first article. The method further includes contacting and securing the surface of the first article with the surface of the second article. The two articles exhibit substantially no corrosion following exposure to a corrosive environment under standard GMW 17026 for a 15 year simulated test.