What Causes Spark Plug Rust?

[VanLukas]

Spark plug rust occurs due to the following reasons: the engine has been submerged in water or subjected to prolonged high-pressure water washing, allowing water to seep into the upper part of the spark plug through the gaps in the ignition coil, leading to rust formation. Spark plugs are installed on the side or top of the engine. In early designs, spark plugs were connected to the distributor via spark plug wires. However, over the past decade, most car engines have transitioned to a direct connection between the ignition coil and the spark plug. How spark plugs work: The spark plug's ground electrode is connected to the metal shell, which is threaded into the engine block via the cylinder head. The insulator primarily serves to isolate the metal shell from the center electrode. The terminal nut is the part of the spark plug that contacts the high-voltage coil. When current passes through the terminal nut and the center electrode, it ionizes the medium between the center electrode and the ground electrode, generating a spark that ignites the air-fuel mixture in the cylinder.