Corrosion occurs in different ways. Electrochemical corrosion is through oxidation (forming a galvanic cell), while chemical corrosion is an oxidation reaction (metals in direct contact with air). Chemical Corrosion: The process of corrosion (oxidation) of metals under non-electrochemical action. Usually refers to corrosion caused by pure chemical action in non-electrolyte solutions and dry gases.
Electrochemical corrosion: iron and oxygen form two electrodes to form a corrosion galvanic cell. Because the electrode potential of iron is always lower than that of oxygen, iron is the anode and is corroded.
