Corrosion Prevention and Cathodic Protection

The issue of corrosion protection has been discussed for many years, yet it has never been given the importance it deserves. In recent years, with the European Union accession process, the imposition of foreign standards and foreign investors, and the increase in the number of well-trained professionals in our country, it has gradually begun to reach its rightful position. While the economic loss caused by corrosion is around 1% of GDP in developed countries, this rate reaches up to 5% in underdeveloped and developing countries. This ratio represents a level of resource loss that our country cannot afford. In external lightning protection and grounding installations, corrosion poses a major problem in terms of both system lifetime and reliability. Especially lightning rods and grounding installation materials produced outside standards quickly corrode and jeopardize system reliability.

A PV plant protection damaged due to corrosion

As electrical engineers, our policy of rejecting non-standard production once again comes to the forefront at this point. The deterioration of materials over time due to environmental effects is defined as corrosion. The material group most affected by corrosion is metals, due to their high tendency for electrochemical reactions. The corrosion resistance of metals depends on their affinity for oxygen. Metals that are stable in their free state (such as titanium) have higher corrosion resistance, while metals with higher oxygen affinity (such as iron) tend to oxidize more easily. Although oxygen affinity is the primary criterion, many secondary factors also exist. For example, aluminum has high corrosion resistance due to its strong affinity for oxygen. The surface of aluminum oxidizes very quickly, and once fully oxidized, oxidation stops, preventing deeper layers from corroding. In common language, the corrosion of iron is called rusting. Rust is a corrosion product with the formula Fe(OH)₂. Among all metal corrosion types, iron corrosion is the most critical and dangerous. Ease of production and low cost have made steel and iron widely used. Especially in pipelines and tanks, metals are coated to protect against corrosion; however, if damage occurs at any point of the coating, corrosion begins rapidly from that point.

Corrosion of a pipe used in an industrial facility

One of the most important factors causing corrosion is material selection. If rules are not followed in installations built outside standards, corrosion is inevitable and maintenance intervals become shorter. Another cause of corrosion is the use of metals with different potentials together, which initiates and accelerates corrosion. A common mistake is using stainless steel bolts and clamps on steel sheet roofs or facades, causing galvanic corrosion. In such cases, fasteners must be insulated with plastic washers. Another factor is uneven oxygen concentration dissolved in soil. Systems placed side by side under different ventilation conditions may act as anodes and cathodes, causing electrochemical corrosion. Additionally, areas with low soil resistivity have higher conductivity, accelerating corrosion mechanisms. Research shows that one of the most common causes of corrosion is the potential difference between coated and uncoated metal. If the coating is damaged due to workmanship errors, those areas become anodic and corrode rapidly. This localized corrosion can be prevented with proper measures.

In summary, the following measures are recommended to protect installations against corrosion:

1- Use of products manufactured within standards (TS EN 62305, EN 50164-1-2…)

2- Proper material selection: choosing materials suitable for the operating environment and avoiding galvanic couples is the most important preventive measure.

3- Scientifically applied coatings: epoxy, bitumen, polyethylene, galvanization, etc., isolate metal from the environment and prevent electrochemical corrosion.

4- Correct design: considering corrosion risks during design and taking preventive measures. For example, using corrosion tape at connection points in grounding projects is effective.

The most effective and widely used method against corrosion is cathodic protection, based on electrochemical corrosion theory. Cathodic protection forces the metal to behave as a cathode, either by pairing it with a more active metal (sacrificial anode) or by applying external current. Galvanic anodes dissolve over time and must be replaced periodically. In impressed current systems, the protective current is supplied externally. Common anode materials are zinc, aluminum, magnesium, while Fe-Si, Pb-Sb-Ag, and Ti-based anodes are used in impressed current systems.

Cathodic Protection changes the potential of the corroding metal, forcing it to behave as a cathode. This method is called IMPRESED CURRENT CATHODIC PROTECTION. Another method uses a more active metal as an anode, called GALVANIC ANODE CATHODIC PROTECTION. The aim is to polarize the metal negatively below a certain potential curve, ensuring continuous current flow. Measurements are typically made using a Copper/Copper Sulfate reference electrode.

Under these conditions, cathodic protection is ensured below -850 mV for iron and -250 mV for copper. Achieving minimum potential at every point in contact with the electrolyte is essential. Corrosion and cathodic protection are critical scientific topics for lightning protection and grounding systems. Preventing non-standard production and installation is vital, as corrosion reduces both system reliability and life safety.