# What are the factors that affect the corrosiveness of an acid?

Acids are usually corrosive but what determines this? Is it the concentration of the acid or strength of the acid ($K_a$ value)?

• Without saying against which substance/surface the corrosiveness is asked for, the question does not make much sense. And an answer is even less thougtful. – Georg May 11 '14 at 13:18

Corrosiveness of an acid is a more complex concept, of course the concentration of the acid and the strength of the acid are two main factors that determinate the success of the corrosion reaction. For example this is the Pourbaix diagram of iron both concentration and $K_a$ determine the pH of the solution so if this is higher then about 9 the metal is passivate and you can't have any corrosion.