Question

In hydrogen evolution type of corrosion with respect to hydrogen electrode which of the following is correct ?

• A. the metal with more negative SRP value under the given conditions
• B. the metal with more positive SRP value under the given conditions
• C. the metal with both negative and positive SRP values
• D. All the above

Answer 1

The correct option is A the metal with more negative SRP value under the given conditions

Any metal lying below hydrogen electrode will reduce $H^{+}$ ions to give $H_2$ gas, while any metal lying above hydrogen will not reduce $H^{+}$ ions.

Thus metals like $Fe,Zn,Cd$ etc lying below hydrogen with more negative $SRP$ capable of reacting with dilute acids while metals like $Ag,Cu$ etc which lie above hydrogen electrode, can not evolve hydrogen with dilute acids.