Electrical Contact Element Corrosion Protection
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Solution Overview
Problem
Aluminium electrical wiring in vehicles is prone to oxidation, leading to reduced conductivity and potential malfunctions due to the formation of an insulating aluminium oxide layer, and galvanic corrosion when in contact with copper, which compromises the quality of electrical contacts over time.
Innovation Solution
An electrical contact element with a coating structure that includes a first layer of tin, a second layer of zinc (acting as a sacrificial anode) only in specific regions, and an optional third layer of a copper-zinc alloy, where the zinc layer is absent in the region ensuring optimal conductivity, thereby preventing corrosion and maintaining electrical contact quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If aluminium is used for electrical wiring to reduce vehicle weight, then vehicle weight is reduced, but oxidation resistance deteriorates leading to reduced conductivity
Solution Approach 1:
The electrical contact element uses an intermediary material (copper or copper alloy) with noble corrosion properties to connect the aluminium electrical line to the mating contact element. The tin and zinc coating layers act as protective intermediaries that prevent direct oxidation of the copper, while the copper itself provides excellent electrical conductivity and oxidation resistance at the contact interface.
2Reliability
If copper is used in electrical contact elements, then oxidation resistance is improved, but galvanic corrosion occurs when in contact with aluminium
Solution Approach 1:
The tin and zinc coating layers serve as intermediary protective barriers between the copper sheet metal and the aluminium electrical line. These layers prevent direct galvanic contact between dissimilar metals, thereby eliminating galvanic corrosion while allowing the copper to maintain its oxidation resistance properties.
Solution Approach 2:
The zinc layer acts as a sacrificial anode that preferentially corrodes to protect the copper and aluminium from galvanic corrosion. This disposable layer consumes itself through controlled corrosion, preventing harmful galvanic effects while protecting the valuable copper contact element.
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 protects against corrosion while maintaining optimal electrical conductivity by selectively applying the sacrificial zinc layer, ensuring the longevity and reliability of electrical contacts in vehicle wiring systems.
Implementation Method 1
When aluminium and copper are in contact in the presence of an electrolyte such as salt containing water, galvanic corrosion will occur due to the rather large difference in the standard electrode potentials of aluminium and copper
Implementation Method 2
The material of the additional layer thus exhibited the lowest standard electrode potential of all layers and therefore would be preferably oxidized, i.e. the additional layer consisted of an easily corrodible material. By corroding, the additional layer protects not only the intermediate layer but also the electrical contact element and the electrical line against corrosion
Implementation Method 3
aluminium is prone to oxidation, when exposed to oxygen from ambient air, which will create a thin layer of electrically insulating aluminium oxide
Data Source
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Figure 3a~3d
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AI summary
The invention relates to an electrical contact element comprising a sheet metal made of a sheet metal material and having a first region and a second region, wherein each one of the first and second regions is coated with a coating including a first layer containing a first material having a lower standard electrode potential than the sheet metal material, characterized in that in the first region, the coating includes a second layer which is absent in the second region, wherein the second layer is arranged underneath the first layer and contains a second material having a lower standard electrode potential than the first material.