Vehicle Joint Edge Sealing for Dissimilar-Metal Corrosion Control
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Solution Overview
Problem
In vehicle assembly processes, structural adhesives used to join dissimilar metal parts can lead to gaps due to vibration, allowing electrolytes to cause galvanic corrosion, and existing sealants may not effectively seal all edges of the joint, especially when some edges are inaccessible to application robots.
Innovation Solution
A method involving the application of a structural adhesive and a sealant to the edges of components before joining, with a sealer applied afterwards to create a comprehensive seal around the adhesive, using a dispensing tool with separate nozzles for each material to ensure thorough coverage and prevent mixing, and a dust sealer to seal exterior edges, forming a closed volume that inhibits water intrusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mastic sealant is applied only at accessible edges using robots, then application efficiency is improved, but corrosion protection is worsened due to unsealed restricted edges
Solution Approach 1:
The sealing process is divided into two distinct segments: (1) robot application of mastic sealant at accessible exterior edges, and (2) manual application of dust sealer at restricted interior edges. This segmentation allows each method to be applied where it is most effective, maintaining productivity while ensuring complete corrosion protection.
Solution Approach 2:
The dust sealer acts as an intermediary material that complements the mastic sealant. While mastic provides primary sealing at accessible edges, the dust sealer serves as a secondary sealing layer at restricted edges, together forming a complete protective barrier against corrosion.
2Reliability
If mastic sealant is applied at all edges, then corrosion protection is improved, but device complexity increases due to need for specialized application equipment
Solution Approach 1:
Different sealing materials and methods are applied to different locations based on their specific requirements: mastic sealant is applied at exterior accessible edges where robot application is feasible, while dust sealer is applied at interior restricted edges where manual application is necessary. This local differentiation optimizes both protection and equipment simplicity.
Solution Approach 2:
The invention accepts that certain edges require manual application of dust sealer rather than automated robot application of mastic. This trade-off uses a simpler, more versatile sealing material (dust sealer) for difficult-to-reach areas, avoiding the need for complex specialized application equipment while maintaining adequate protection.
3Adaptability or versatility
If gaps form in structural adhesive, then assembly flexibility is improved, but water infiltration increases causing galvanic corrosion
Solution Approach 1:
The mastic sealant and dust sealer are applied in advance to the edges of the joint before final assembly, creating a protective barrier that cushions against future water infiltration. This pre-application of sealing materials prevents electrolyte ingress that would otherwise cause galvanic corrosion, while allowing the structural adhesive to maintain its flexibility for assembly adjustments.
Solution Approach 2:
The sealing system uses a composite approach combining two different sealing materials: mastic sealant (a rubber-based anti-flutter sealant) for exterior edges and dust sealer (a flexible sealing compound) for interior edges. This composite sealing strategy provides comprehensive protection against water infiltration while allowing the structural adhesive to maintain assembly flexibility.
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
This method effectively seals all edges of the joint, preventing electrolyte ingress and corrosion, even in areas inaccessible to application robots, by using a combination of structural adhesive, sealant, and dust sealer to create a watertight seal around the adhesive, ensuring the longevity and integrity of the vehicle assembly.
Implementation Method 1
the adhesive initially occupies the space between the surfaces of the welded parts. Eventually however, the structural adhesive can begin to pull away from one or both of the surfaces during the lifetime of the vehicle due to vibration or other reasons, and one or more gaps forms between the welded parts by which electrolyte (e.g. water) enters between the two parts. The electrolyte can then contact surfaces of the two parts that are not e-coated and therefore cause galvanic corrosion.
Implementation Method 2
a structural (crash toughened) adhesive may be applied to a joint in between the two parts
Implementation Method 3
a mastic (anti-flutter sealant) or dust sealer may be subsequently applied along an edge of the welded joint so as to block the gaps that may form in the structural adhesive and thereby isolate the uncoated surfaces of the two parts from water
Data Source
AI summary
A method of joining first and second vehicle components to make an assembly includes applying structural adhesive and mastic to the first component. The first and second component may be made of different metals, and are brought together and joined at an interface using a linkage. Thereafter, the structural adhesive and mastic are cured. The mastic seals an interior edge of the interface, which is located at an interior of the assembly. A dust sealer is applied and cured to seal the exterior edge of the interface, which is located at an exterior of the assembly. The method results in sealing of all the edges around the entire perimeter of the interface, thus inhibiting water intrusion into the interface and possible corrosion resulting therefrom.