Expert Tips

Output Voltage Ratings

The DC output “ratings” for Cathodic Protection (CP) rectifiers refer to the DC output voltage and current capacity of the rectifier.  Output voltage ratings are typically between 5 and 125 volts, while current ratings range between 5 and 400 amperes. 

Physical Appearance
High potential (HP or M1) magnesium anodes and standard potential (AZ) magnesium anodes look alike.  There is very little, if any, physical difference between the two anodes.  While there is certainly a difference in the chemistry or alloy and their performance, you cannot tell the difference by just looking.

The term used for measuring the distance between two circles, holes, or other round objects, is center-to-center. This is the dimension or distance from the center of one circle to the center of a second circle.

In the Cathodic Protection (CP) industry, we are required to use several types of reference electrodes to measure the voltage differential between the structure being evaluated and the reference electrode. The types and configurations vary, and the details here refer to both portable and stationary reference electrodes.

Rectifier Cabinet Materials:
Steel is most often used for air-cooled rectifier cabinets due to its relative durability and cost. Aluminum and stainless steel are also available but at a greater cost. Oil-cooled cabinets are almost always (if not always) heavy-gauge steel for durability purposes.

Common Air-Cooled Rectifier Mounting Techniques:

Most air-cooled rectifier cabinets will mount on a steel pole or wood post, which is common in rural areas. Standard, air-cooled rectifier cabinets typically include a mounting channel that can be bolted to the pole or post, and the channel fits the contour of the pole or post for mounting ease.

What Type of Rectifier Cooling is best? Air or Oil?
Cathodic protection (CP) rectifiers generate heat due to the loss of energy as a result of converting AC power to DC. This is caused by the relative inefficiency of the internal components, such as the transformer and diodes. Therefore, this heat must be moved away from the rectifier components.

Corrosion technicians conduct routine operational status checks on Cathodic Protection (CP) Systems to ensure that the system is providing adequate levels of protection. Many common systems can include multiple 2-wire, magnesium anode test stations (1 wire for the anode and one wire for measuring Pipe-to-Soil (P/S) potentials) with simple 2-wire P/S test stations between the anode test stations. Normal potential readings should be between -0.950 and -1.150 volts with respect to a CuSO4 reference electrode along the pipeline.