SPARK PLUG AND MAIN FITTING FOR SPARK PLUG

摘要

The adhesiveness of a nickel-plated layer to a main fitting is improved, and a corrosion resistance improvement effect is sufficiently demonstrated as a result of providing the nickel-plated layer. A spark plug (1) is provided with a main cylindrical fitting (3) that extends in the axis line (CL1) direction, and a nickel-plated layer (31) that comprises metals consisting primarily of nickel, and that covers the outer surface of the main fitting (3). In a grayscale image with 256 gradations, in which, when a cross-section that intersects with the outer surface of the nickel-plated layer (31) is observed by transmission electron microscope according to a 200 kV accelerating voltage, black is considered to be 0 and white is considered to be 255, the average value of the 256 gradations of the grayscale image is from 170 to 230.