Expert Tips

Interrupted testing has become more common, and many conventional tap-controlled rectifiers weren’t designed to interrupt easily. Traditional configurations often require a portable interrupter and heavy temporary cabling, which can be time-consuming and can even change rectifier output during the test.

When applying protective coatings, temperature and humidity matter. If the surface temperature of a structure is too close to the dew point, condensation can form - leading to poor coating adhesion, blistering or premature failure.

Why it matters

A properly applied coating is your first line of defense against corrosion. Moisture on the surface of the structure to be coated, even invisible condensation, prevents coatings from bonding effectively.

Coating performance is heavily influenced by surface condition at the time of application, and “dry-looking” steel can still be at risk. When substrate temperature approaches the dew point, micro-condensation can form and lead to loss of adhesion, blistering and premature breakdown.

Deciding which cable insulation to use for impressed current anodes depends on installation parameters.  A single layer of HMWPE insulation is a good choice for anodes but is not chemically resistant. Therefore, the insulation can deteriorate when exposed to certain chemicals, such as chlorine gas, causing premature cable failure.   Adding a primary layer of Halar provides a very chemically resistant protective layer to the copper cable. It is the best choice when significant chlorine gas is produced in the anode well and in contact with anode cable.

Most Cathodic Protection (CP) technicians understand the purpose and operating features of CP rectifiers. However, when the CP system goes down, troubleshooting a CP rectifier may require some help.

The following provides a basic understanding of the function of the CP rectifier and some basic troubleshooting tests that can identify many of the common rectifier problems.

The following are considerations when selecting the type of cathodic protection (CP) system for a newly installed, existing buried or submerged structure.

Surface Area of Exposed Metal
The size and cost of most CP systems are controlled by how much CP current is required to effectively protect the exposed metal in contact with the electrolyte (soil or water). Therefore, one of the first considerations when designing or selecting a CP system is the surface area of metal exposed to the electrolyte.

In the corrosion industry, “coupons” are used in the fight against corrosion, but the term coupon is used interchangeably in corrosion monitoring. In fact, there are two general types of corrosion monitoring coupons used for entirely different purposes.

Cathodic Protection Coupons
These metallic coupons of a specific size are used to assess the effectiveness of cathodic protection (CP) systems. They are typically made of the same metal as the structure being protected. CP coupons are buried adjacent to the structure under protection, and a coupon cable or cables are routed to an above-ground test station where CP professionals can conduct CP testing. The CP coupon, which is bare metal, represents a coating defect or “holiday” in the structure’s protective coating

During a typical cathodic protection (CP) field survey, the CP technician must make effective electrical connections to the structure under test and other metallic components.

Often, the technician will encounter an existing above-ground test station where a conductor (cable) is permanently attached to the structure under test and the other end is terminated to the test station panel. In this case, the connection to the structure is already made and is typically effective.

When an existing CP system requires review and/or testing, the work will be to determine if the system is working correctly and/or to troubleshoot system issues. Before the fieldwork starts, it is important to review any available documentation or historical data describing the type of CP equipment and itsperformance.

Dielectric coatings play a crucial role in protecting buried pipelines from various forms of corrosion and degradation.