Cause corrosion is a process in which metal objects are damaged due to chemical reactions. This can be caused by exposure to water, oxygen, or other corrosive substances. The two crossword solutions, EAT and GNAW, refer to the way in which corrosion can occur. EAT is an acronym for Electrolytic Action of Tin, which is a type of corrosion that occurs when tin is exposed to water. GNAW is an acronym for Galvanic Action of Nickel and Water, which is a type of corrosion that occurs when nickel is exposed to water. Both types of corrosion can cause damage to metal objects over time.