NEIEP Mechanics Practice Exam

Using current from a rectifier, through an anode, then to the cylinder describes which type of corrosion protection system?

1. Galvanic System

2. Impressed Current System

3. Cathodic Protection

4. Passive Protection

The correct answer is: Impressed Current System

The answer is that an impressed current system is designed to protect structures from corrosion by utilizing an external power source to drive a current through the anode to the cathode (or the structure needing protection). In this type of system, the rectifier converts alternating current (AC) to direct current (DC), which flows through the anode and into the surrounding electrolyte (like water or soil) to reach the structure being protected. In an impressed current system, the current flow effectively alters the electrochemical potential of the structure, making it more noble (or less susceptible to corrosion) compared to its surroundings. By continuously supplying an external current, this method can offer more robust and controllable protection over larger areas or under more severe corrosive conditions than other systems. Other options, though related to corrosion protection, differ in their mechanisms. For example, a galvanic system uses two different metals in contact where a spontaneous electrochemical reaction occurs, providing protection without the need for external power. Cathodic protection is a broader term that encompasses both impressed current and galvanic systems. Passive protection generally involves physical barriers (like coatings) rather than electrochemical methods.