EROSION MECHANISMS OF AUTOMOTIVE SPARK PLUG ELECTRODES

Scanning electron microscopy and microchemical analyses were conducted to determine the electrode erosion mechanisms of two different spark plugs, platinum-tip and nickel-alloy, tested under various environments in both bench and vehicle tests. The electrodes were shown to have eroded by different mechanisms, depending on the electrode materials and the operating environments. In the bench test, the platinum center electrode is eroded primarily by ejection of molten platinum particles through a recoil force mechanism, and, to a lesser degree, by metal vaporization. The nickel-alloy center electrode was eroded by ejection of molten oxide particles from the oxide layer on the electrode surface. The nickel-alloy side electrodes are eroded by metal vaporization due to electrode-ion bombardment. In vehicles using unleaded fuels, the nickel-alloy center electrode is rerded by vaporization of the top compound layer, and by oxidative recession of the base metal. In vehicles using leaded fuel, the nickel-alloy electrodes are eroded mainly by chemical corrosion. In vehicles using unleaded fuel with MMT (Methycyclopentadienyl manganese tricarbonyl) additive, the platinum center electrode is eroded by separation of platinum grains due to grain boundary corrosion. The nickel-alloy center electrode is eroded by particle ejection from the surface compound, and by oxidative recession of the base metal; the side electrode is eroded by surface vaporization and base metal oxidation.

• Supplemental Notes:
  • Presented at the SAE Congress and Exposition, Detroit, 27 February-3 March 1978.
• Corporate Authors:

  Society of Automotive Engineers (SAE)

  400 Commonwealth Drive
  Warrendale, PA  United States  15096
• Authors:
  • Young, C T
  • Grimes, D A
• Publication Date: 1978

Media Info

• Features: References;
• Pagination: 19 p.

Subject/Index Terms

• TRT Terms: Corrosion; Electrodes; Erosion; Nickel alloys; Platinum; Spark plugs
• Old TRIS Terms: Electrode erosion
• Subject Areas: Safety and Human Factors;

Filing Info

• Accession Number: 00395655
• Record Type: Publication
• Source Agency: National Highway Traffic Safety Administration
• Report/Paper Numbers: SAE 780330, HS-025 425U
• Files: HSL, USDOT
• Created Date: Jun 30 1985 12:00AM