Why does the use of oiled sand beneath tank bottoms not eliminate the need for cathodic protection?

Why does the use of oiled sand beneath tank bottoms not eliminate the need for cathodic protection?

• A. The oiled sand has higher resistivity
• B. The sand cannot conduct electrical current
• C. The oil acts as an insulator
• D. It creates a vapor barrier trapping contaminants

Answer: (A)

The oiled sand beneath tank bottoms does not eliminate the need for cathodic protection because oiled sand typically has higher resistivity compared to other types of soil or media. Cathodic protection is utilized to mitigate corrosion of the tank’s steel structure, and its effectiveness is heavily dependent on the electrical conductivity of the surrounding medium. If the resistivity is high, it can impede the flow of protective current, thereby reducing the adequacy of the cathodic protection system. In this context, higher resistivity means that the oiled sand may not allow sufficient current to flow effectively. Consequently, even with the presence of oiled sand, the tank could still be vulnerable to corrosion, necessitating an ongoing requirement for cathodic protection measures to enhance the integrity of the tank structure over time.

The oiled sand beneath tank bottoms does not eliminate the need for cathodic protection because oiled sand typically has higher resistivity compared to other types of soil or media. Cathodic protection is utilized to mitigate corrosion of the tank’s steel structure, and its effectiveness is heavily dependent on the electrical conductivity of the surrounding medium. If the resistivity is high, it can impede the flow of protective current, thereby reducing the adequacy of the cathodic protection system.

In this context, higher resistivity means that the oiled sand may not allow sufficient current to flow effectively. Consequently, even with the presence of oiled sand, the tank could still be vulnerable to corrosion, necessitating an ongoing requirement for cathodic protection measures to enhance the integrity of the tank structure over time.