Pitting corrosion is a type of corrosion that attacks a local area of the metal and eventually leads to the formation of holes in the metal. Pitting corrosion can lead to stress corrosion cracking, an example for which is the collapse of the Silver Bridge in West Virginia, USA in 1967. This type of corrosion generally occurs when a small area is affected by the environment and becomes anodic. Meanwhile, another area in the metal acts as a cathode. This leads to a type of galvanic corrosion which begins at the surface of the metal but can spread downwards and eventually lead to the structural failure of the metal.