Question

Using fundamental thermodynamics, and ignoring reaction kinetics, explain which of the following materials is most susceptible to corrosion in fully aerated (O2 saturated) seawater (pH = 6.5) -- aluminum metal, iron metal, glass (silicon dioxide), or gold.

Answer 1

Aluminium is most susceptible to corrosion. because, it is most reactive element as per the electrochemical series.

The Reduction potential is -1.67 V.

This makes aluminium act as powerful reducing agent and itself undergoes oxidation. hence easily at normal conditions of temperature, Aluminium easily reacts with oxygen and the reaction becomes spontaneous.

Therefore, Aluminium shows more susceptible towards corrosion.

G⁰ = -nFE

Where, E = EMF of the cell.

When G is -ve the reaction is spontaneous.

The reactions involving aluminium G is -ve and always spontaneous.

Fe, +0.77V

Au +1.68

SiO2 is -0.909.