How Do You Test For Cathodic Protection?

What are the two types of cathodic protection systems?

There are two types of cathodic protection, galvanic protection and impressed current.

A galvanic cathodic protection system for USTs, consists of sacrificial anode(s) fixed to the UST during manufacturing of the UST, and provides specified wiring for an inspection station installed near the surface of the ground..

What is the principle of cathodic protection?

Cathodic protection prevents corrosion by converting all of the anodic (active) sites on the metal surface to cathodic (passive) sites by supplying electrical current (or free electrons) from an alternate source. Usually this takes the form of galvanic anodes, which are more active than steel.

What’s inside a rectifier?

The rectifier circuit, which is typically made from a set of cleverly interlocked diodes, converts alternating current to direct current. In household current, the voltage swings from positive to negative in cycles that repeat 60 times per second. … Overall, voltage rectified by a single diode is off half of the time.

What is cathodic testing?

A cathodic protection inspection is the only way to verify sacrificial anode systems are working properly. Sacrificial systems rely on a large number of buried anodes to prevent corrosion. These anodes are attached to the buried steel and over time lose their connection or have lower energy output.

How do you measure anode resistance?

Anodic resistance is measured using a triode tube that is presented to a transformer (output) or other types of stage within a concrete circuit. In this case, the anode resistance can be measured by driving tiny unloaded signals into it. This is done to measure the output voltage.

Which metal is used for cathodic protection?

Zinc, aluminium and magnesium are the metals commonly used as anodes. Read more about the galvanic series and nobility of metals. The most active metal (whis also is the less noble) becomes the anode to the others, and sacrifices itself by corroding (giving up metal) to protect the cathode.

What is the difference between sacrificial protection and cathodic protection?

The main difference between the two methods is that the impressed current cathodic protection uses an external power source with inert anodes while the sacrificial anodes cathodic protection uses the naturally occurring electrochemical potential difference between different metallic elements to provide protection.

What is a cathodic protection test station?

A cathodic protection test station is an integral part of any pipeline cathodic protection system. The cathodic protection test stations can be supplied as a kit with the cabling, reference electrodes and thermite weld equipment needed to complete the installation. …

How often must cathodic protection rectifier readings be recorded?

every 60 daysA: It is recommended that you check your impressed current system every 30 days and the results of the rectifier output recorded. Although you are only required to monitor and record the rectifier readings every 60 days for proper operation, it is easier to remember to check monthly.

How long does cathodic protection last?

10-20 yearsThe anodes remain reactive through their lifetime (10-20 years typically) increasing current when the resistivity decreases due to corrosion hazards such as rainfall, temperature increases or flooding.

Why do rectifiers fail?

The common reasons for a diode failure are excessive forward current and a large reverse voltage. Usually, large reverse voltage leads to a shorted diode while overcurrent makes it fail open. Let’s see how a shorted diode will affect a full-wave rectifier.

Is cathodic protection necessary?

In summary, cathodic protection is a commonly used method of protecting steel structures, yet can be costly and require routine maintenance and replacement. Products that provide a protective layer with zero reactivity are more likely to extend the life of steel structures and create a nonreactive layer of protection.

What is impressed current cathodic protection?

Impressed current cathodic protection (ICCP) is a type of system usually applied where there are elevated current requirements for protection against corrosion. This is used in cases where the driving voltage is higher than the galvanic system or if there is a need for increased system control.

How do you test anodes?

Anode Testing ProcedureUsing a digital voltmeter select the 2 volt DC scale, Contact red test lead to the tank test point or an uncoated metallic area of the tank, preferably to the uncoated fill pipe. … Contact the black test lead from the meter to a charged reference electrode.More items…•

How does a cathodic protection rectifier work?

Cathodic protection rectifiers are the external power source used in impressed current cathodic protection systems (ICCP) to convert alternating current (AC) to direct current (DC). In ICCP systems, current is discharged off of the anode and onto the structure to prevent corrosion.

What is the difference between cathodic and anodic protection?

Cathodic protection converts all anodic areas on a metal surface to cathodes so that corrosion ceases. … Anodic protection, on the contrary, makes the entire metal surface an- odic-so anodic that the metal completely passivates. Obviously, then, this technique is limited to metals that can form protective passive films.