THV Isolator for Galvanic Corrosion Protection
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Solution Overview
Problem
Dissimilar metal substrates mechanically fastened together are prone to galvanic corrosion, which existing methods have not adequately addressed, particularly in weight-reduced materials used in the transportation industry.
Innovation Solution
An isolation barrier or isolator comprising a non-permanently compressible backing layer and an uncured adhesive layer, which is resistant to polar solvents and electrically insulative, is placed between dissimilar substrates to prevent ion transfer and corrosion, while being designed to remain fixed in place to avoid wear and allow for easy disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If dissimilar metal substrates are mechanically fastened together to reduce weight, then weight reduction is achieved, but galvanic corrosion risk increases
Solution Approach 1:
The patent introduces an isolator as an intermediary component between dissimilar metal substrates. This isolator includes a non-permanently compressible backing layer and an uncured adhesive layer that cures to bond the substrates together while preventing galvanic corrosion through electrical insulation and physical separation, thus eliminating direct metal-to-metal contact that causes corrosion.
2Strength
If an adhesive layer is used to bond substrates, then bonding strength is improved, but energy consumption increases due to curing process
Solution Approach 1:
The patent applies adhesive only partially - the uncured adhesive layer is applied to only one side of the non-permanently compressible backing layer rather than sandwiching the substrates between adhesive layers. This partial application reduces the total amount of adhesive requiring curing, thereby reducing energy consumption while still achieving sufficient bonding strength for the mechanical fastening application.
3Strength
If adhesive is applied between dissimilar substrates, then bonding is achieved, but risk of permanent bonding increases
Solution Approach 1:
The patent segments the bonding system into three distinct functional layers: a non-permanently compressible backing layer, an uncured adhesive layer applied to one side of the backing, and the dissimilar metal substrates. The backing layer acts as a mechanical stop and isolation barrier that prevents the adhesive from bonding the substrates directly to each other, allowing for future disassembly while maintaining bonding strength during service.
4Reliability
If isolator remains fixed between substrates, then corrosion protection is maintained, but wear of isolator may occur
Solution Approach 1:
The patent employs a non-permanently compressible backing layer that can elastically deform under compression from the substrates but returns to its original shape. This flexibility allows the isolator to accommodate thermal expansion, vibration, and minor misalignments without experiencing permanent deformation or wear, thereby maintaining its corrosion protection function throughout the service life of the assembly.
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 prevents galvanic corrosion between dissimilar metal substrates by blocking ion transfer and withstanding shear stress, while allowing for easy disassembly and serviceability, thus enhancing the durability and reliability of lightweight structures.
Implementation Method 1
At least one of the cured adhesive layer and the backing layer is, and preferably both are, resistant enough to polar solvents (e.g., water) and mixtures thereof so as to prevent the transfer of electrolytes (e.g., water transported metal ions) from passing all the way through its thickness
Implementation Method 2
Optionally, at least one of the cured adhesive layer and the backing layer is, and preferably both are, electrically insulative, when measured according to ASTM D57-99
Data Source
AI summary
An isolator for protecting adjacently located dissimilar material substrates from galvanic corrosion. The isolator includes a backing layer having opposite major surfaces and a thickness, and an optional uncured adhesive layer having one major surface bonded to one of the major surfaces of the backing layer and another major exposed surface for being adhesively bondable to a surface of one of the dissimilar material substrates. In its cured state, the adhesive layer and the backing layer are each not permanently compressible. At least one or both of the cured adhesive layer and the backing layer is polar solvent resistant enough to prevent polar solvent transported metal ions from passing all the way through its thickness. In preferred embodiments the backing layer comprises a tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride (THV) material, and the adhesive layer comprises an epoxy resin.