Spark Plug Nickel Plating Uniformity and Corrosion Resistance
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Solution Overview
Problem
Spark plugs face issues with non-uniform nickel plating thickness, leading to stress concentration and peeling off of the plated layer, which compromises corrosion resistance, especially in regions difficult for electric current to flow during the plating process.
Innovation Solution
A nickel plated layer with a uniform thickness is achieved through electrolytic nickel plating treatment, where carbon and phosphorus/boron atoms are added to the plating bath to promote uniformity, and a chromate layer or rust prevention oil is applied to enhance corrosion resistance, with specific thickness and concentration ranges to prevent peeling and ensure effective corrosion protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrolytic nickel plating treatment is performed on the metal shell, then corrosion protection is achieved, but the plated layer thickness becomes non-uniform in regions difficult for electric current to flow
Solution Approach 1:
The patent applies parameter changes by controlling the atomic concentration of carbon elements (1.0-10.0% at depth where Ni concentration is 80%) and controlling plated layer thickness (0.3-2.0μm minimum, 15μm maximum) to achieve both uniform plating and corrosion resistance. This resolves the contradiction by optimizing plating parameters to ensure adequate thickness even in regions difficult for electric current to flow.
2Strength
If the nickel plated layer thickness is reduced to minimize stress, then peeling is suppressed, but corrosion resistance deteriorates
Solution Approach 1:
The patent optimizes the plated layer thickness parameters (minimum 0.3μm, maximum 15μm, difference between max and min 5.5μm or less) to find the balance point where the layer is thin enough to minimize stress concentration and peeling, yet thick enough to provide adequate corrosion protection. This parameter optimization resolves the contradiction between peeling resistance and corrosion resistance.
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 ensures improved corrosion resistance by maintaining uniform nickel plating thickness and reducing stress concentrations, thereby preventing peeling and enhancing the longevity of the spark plug's protective layer.
Implementation Method 1
a nickel plated layer is formed in an electrolytic nickel plating treatment on the metal shell
Implementation Method 2
the atomic concentration of C elements is 1.0% or more and 10.0% or less at a depth at which the atomic concentration of Ni elements is 80%
Data Source
Figure 1
Figure 2(A)~2(D)
Figure 3
AI summary
To provide a technology of improving the corrosion resistance of a spark plug. A spark plug 100 includes a metal shell 1 on the outer surface of which a nickel plated layer is formed as a protective surface film. The nickel plated layer is such that when the atomic concentrations of constituent elements are measured in a depth direction by an X-ray photoelectron spectroscopy (XPS), the concentration of carbon atoms is 1.0% or more and 10.0% or less at a depth at which the atomic concentration of Ni elements is 80%.