| 摘要 |
<p>A spark plug is provided. A recess part is disposed at the rear end of a terminal electrode and a nickel layer is formed at the rear end of the terminal electrode. In the spark plug, the corrosion resistance of the terminal electrode is fully enhanced and inhibition for peeling of the nickel layer is more reliable. The spark plug (1) comprises: an insulation electrotechnical porcelain (2) provided with an axis hole (4) penetrating along the axis direction (CL1); and the terminal electrode (6), wherein the rear end of the terminal electrode is inserted into the axis hole (4) in a state that the rear end of the terminal electrode protrudes out from the rear end of the insulation electrotechnical porcelain (2). The rear end of the terminal electrode (6) is provided with the recess part adopting the axis direction (CL1) as the depth direction. The nickel layer (35) is disposed on the external surface of the rear end of the terminal electrode (6), and has a thickness of 3-25 [mu]m. In a cross section orthogonal to the external surface of the nickel layer (35), the average section area of crystal grains forming the nickel layer (35) is 50-500 [mu]m<2>.</p> |
