* Exposure to moisture: The oil dipstick is located in the engine bay, which is exposed to moisture from the air and from rain. If the dipstick is not properly sealed, moisture can seep in and cause the metal to rust.
* Contact with oil: The oil dipstick is also in contact with engine oil, which contains corrosive chemicals. These chemicals can attack the metal of the dipstick and cause it to rust.
* Galvanic corrosion: If the dipstick is made of a different metal than the engine block, galvanic corrosion can occur. This type of corrosion occurs when two dissimilar metals are in contact with each other and exposed to an electrolyte, such as water or salt. The more active metal (the one with a lower reduction potential) will corrode while the less active metal will be protected. In the case of a 1989 350 Chevy, the dipstick is usually made of steel, while the engine block is made of cast iron. Steel is more active than cast iron, so it will corrode when the two metals are in contact with each other and exposed to moisture.
To prevent the oil dipstick from rusting, you should:
* Make sure that the dipstick is properly sealed to prevent moisture from seeping in.
* Avoid spilling oil on the dipstick.
* If the dipstick is made of steel, you can apply a rust-resistant coating to protect it from corrosion.
