Chapter 20, Problem 94A

Interpretation Introduction

Interpretation:

A report about the effect of biological effect of rusticle communities on the oxidation of iron is to be written.

Concept introduction:

A rusticle is a formation of rust which is similar in shape to an icicle or stalactite. They occur on iron structures deep underwater.

Answer to Problem 94A

The rusticle is formed from iron containing compounds like iron oxides, carbonates and hydroxides.

Rusticles are spike shaped structures which are formed when iron consuming microbes act on iron and steel structures which are present in the deep ocean. The rusticles act as a home for the iron consuming bacteria and fungi which damages remaining parts of iron and increases the rate of the decay of the structure. The rusticles formed on structures which are submerged, has almost zero dissolved oxygen. The role of the microbes in rusticle formation is very crucial.

From the rusticle growth which have been observed at the titanic, the bow is destroying more slowly than the stern, suggests that there is a catalytic role of the rusticle community in its corrosion.

Explanation of Solution

The deterioration of the bow and stern sections of Titanic was observed. It was found that the bow section of the ship had decayed at a slower rate than the stern section which has been calculated to be about 40 years less then stern of the ship. The reason was the state of the steel at the stern, which was providing better areas for rusticle formation and the growth of metal corroding microbes. And because food was also stored on Titanic in the stern section of the ship, it provided the starting materials to the microbes for rusticle growth.