Electrochemical Corrosion - Corrosion Engineering MCQ Questions

Explanation: Electrochemical corrosion of metals occurs when electrons from atoms at the surface of the metal are transferred to a suitable electron acceptor or depolarizer.

Explanation: Water must be present to serve as a medium for the transport of ions.

Explanation: The most common depolarizers are oxygen, acids, and the cations of less active metals.

Explanation: Corrosion of steel can be inhibited by galvanizing, that is, by coating it with zinc, a more active metal whose dissolution leaves a negative charge on the metal which inhibits the further dissolution of Fe2+.

Explanation: Combination reaction: A+B==>C,
Decomposition reaction: A==>B+C,
Single displacement reaction: AB+C==>AC+B
Double displacement reaction: AB+CD==>AC+BD

Explanation: The Function of an electrolyte is to transfer the ions between anode and cathode. Increase in electrical resistance in electrolyte shows obstruction for the free flow of ions, hence the corrosion rate decreases. Whereas dissolved oxygen, temperature and presence of ferric ions increases the mobility of ions and increases the corrosion rate.

Explanation: Polarization is the potential difference occurred due to the non-equilibrium conditions, due to the change in concentration or temperature. These are classified into three types. They are i) Activation polarization ii) Concentration polarization iii)Resistance polarization.

Explanation: Passivation is the state of metal in which stable films or barriers are formed. These stable films obstruct the contact of corrosive medium to the metal surface. Most of the engineering metals undergo passivation under different atmospheric conditions.

Explanation: Salt bridge is a connection between two half cells used to neutralize the ions with respective opposite charged ions. Usually, strong electrolytes such as KCl along with agar-agar gel are used.

Explanation: Concentration polarization refers to the electrochemical reaction that is controlled by the diffusion of ions in an electrolyte. With an increase in the velocity or agitation of the electrolyte the contact of ions with metal interface increases.