concentration cells and corrosion

Concentration Cells and its types

A concentration cell is shown below

Corrosion is

When a cell is placed in 0.25 M concentrated suger solution, there is no change in it. The concentration of cell sap would be

If the solute concentration is increased inside the cell

Concentration Cells,Nernst Equation on Half Cells

What are the harmful effects of corrosion ? Mention a type of corrosion which is helpful to the metal.