Disadvantage- it weakens the metal
advantage- in some metals it forms a deposit of metal oxide and protects it form further degradation or lossĀ 
Corrosion is highly unwanted and has got many disadvantages but the good thing is that corrosion can be controlled by use of proper materials and maintaining certain conditions. disadvantage of corrosion include loss contamination and deterioration of the apprence of a also get safety health and environmental risks when corrosion occurs, you need to spend more money to avoid corrosion for machines and to maintain it etc.

hope it helps you!!!