Spark Plug Housing Coating to Prevent Corrosion Without Chromium
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Solution Overview
Problem
Current spark plug housings face corrosion issues due to defects in nickel-containing protective layers, which can lead to the formation of harmful hexavalent chromium, and lack sufficient temperature resistance.
Innovation Solution
A corrosion protection layer system comprising a nickel-containing protective layer and a silicon-containing sealing layer, where the silicon sealing layer replaces chromium-containing layers, providing enhanced temperature resistance up to 300°C and preventing hexavalent chromium formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a chromium-containing sealing layer is applied to seal defects, then corrosion protection is improved, but hexavalent chromium may form and pose health risks
Solution Approach 1:
The silicon-containing sealing layer acts as an intermediary material that performs the defect-sealing function previously accomplished by chromium-containing layers. Silicon provides the necessary sealing properties without the harmful hexavalent chromium formation, mediating between the need for defect sealing and the requirement to avoid harmful substances.
Solution Approach 2:
The patent eliminates the harmful aspect (hexavalent chromium formation) while preserving the beneficial function (defect sealing and corrosion protection). By replacing chromium with silicon, the harmful chemical transformations are prevented while the sealing function is maintained or improved, particularly with respect to temperature resistance.
2Temperature
If the housing is exposed to high temperatures, then engine operating conditions are met, but corrosion protection may deteriorate
Solution Approach 1:
The multi-layer composite coating system addresses temperature-related corrosion by combining materials with complementary thermal and corrosion resistance properties. The nickel- and zinc-containing layer provides base corrosion protection while the silicon-containing sealing layer offers superior temperature stability and maintains its sealing function at high temperatures, ensuring corrosion protection is maintained under engine operating conditions.
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 corrosion and maintains a rust-free state in salt spray tests even after exposure to high temperatures, ensuring long-lasting protection without the use of chromium-containing sealing layers.
Implementation Method 1
The protective coating is a nickel and zinc-containing protective layer that is applied to the housing using electroplating
Implementation Method 2
the sealing layer arranged on a nickel- and zinc-containing protective layer contains silicon
Implementation Method 3
these housings still exhibit a rust degree of 0 after 24 hours in the salt spray test
Data Source
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AI summary
The invention relates to a housing (2) for a spark plug (1), having a bore along the longitudinal axis X of the housing (2), the housing (2) comprises an outer side (205) and an inner side (204) and a galavanically applied nickel and zinc-containing protective layer (210) is arranged on at least one part of the outer side (205) of the housing (2). A sealing layer (220), which contains silicon, is arranged on the nickel and zinc-containing protective layer (210).