# Corrosion of metal

Why would a metal corrode more in a lower concentration of nitric acid compared to a higher concentration sulfuric acid? Isn't sulfuric acid suppose to be a stronger acid compared to nitric acid?

## 1 Answer

Sulfuric acid is not as strong of an oxidizer. Nitric acid, particularly when hot, is very strongly oxidizing.

Note that both acids are "strong acids" in that they completely dissociate (at least one proton in the case of sulfuric acid) in water. However, this does not completely determine a compound's ability to oxidize metals. Oxygen and chlorine for example will oxidize many metals very well, and they certainly are not strong acids!

• Thanks @airhuff !! I read on a similar post that nitric acid is a better oxidizing agent because unlike other metal dissolution reactions, the H+ of HNO3 isn't reduced-- the NO3− is. And it was correlated with the reduction potential. How does the reduction potential determine which ion is being reduced? – Vin Jan 16 '17 at 9:51
• It depends on the electronegativity of the metal relative to $\ce{NO3^-}$. For example, Mg, Mn and Zn all reduce $\ce{H+}$ to $\ce{H2}$. The more electronegative metals Ag however reduces $\ce{NO3^-}$ to NO. $\ce{NO3^-}$ is in it's most oxidized state reasonably possible, and more prone than some other acids to being reduced, thus making it a relatively strong oxidezer. – airhuff Feb 9 '17 at 19:34