The Importance of Cathodic Protection in Oil and Gas Industries
Corrosion is likely the most deleterious and hazardous form of damage associated with oil and gas production and transportation. Unfortunately, almost every single aqueous environment can facilitate corrosion, which is defined as a destructive attack upon material by substances in its surrounding environment. The threat of corrosion problems in the oil and gas industries has given rise to protective systems such as cathodic protection, which has proven an invaluable tool for the safeguarding of oil and gas pipelines. Here, we will review some of the most common types of corrosion and demonstrate the importance of cathodic protection in the oil and gas industries.
Sweet Corrosion – CO2 Corrosion
CO2 corrosion has plagued the oil and gas industries for many years. CO2 gas becomes corrosive when dissolved in an aqueous environment. This is because it promotes an electrochemical reaction between the steel pipeline and the aqueous environment. The CO2 mixes with the water, creating carbonic acid and the acidic fluid then corrodes the pipe. This is often referred to as sweet corrosion. CO2 corrosion presents itself in these common forms:
- Pitting-type corrosion
- Mesa attack corrosion
Sour Corrosion – H2S Corrosion
When hydrogen sulfide (H2S) and moisture come in contact with metal, it causes corrosion known as sour corrosion. When hydrogen sulfide is dissolved in water, it becomes acid as well as a source of corrosive hydrogen atoms. These corrosive byproducts are iron sulfides (FeSx) and hydrogen. These are particularly damaging to drilling pipes and result in the following forms of corrosion:
- Stepwise cracking
Oxygen reacts with metal extremely quickly. When it dissolves within drilling fluids, it becomes a major cause of drilling pipe corrosion. Due to the speed at which drilling fluid travels over a pipeline, even small concentrations of oxygen (as low as five parts per billion) will cause constant destruction to the pipeline itself. In fact, the presence of oxygen actually exacerbates the corrosive effects of other acidic gases, including the previously-mentioned CO2 and H2S. The forms of corrosion caused by oxygen include:
- Uniform corrosion
- Pitting-type corrosion
Microbiologically-induced corrosion (MIC) is a form of corrosion caused by bacteria. Bacterial waste often includes CO2, H2S, and other organic acids, increasing the toxicity of the fluids passing through an oil or gas pipeline. It can be identified by the presence of black waste material on the surface of pipelines and it can cause pitting underneath these waste deposits.
The Importance of Cathodic Protection in the Oil and Gas Industries
Cathodic protection is a corrosion-reducing method that minimizes the difference in potential between an anode and a cathode. By applying an electrical current to the structure (an oil or gas pipeline), we protect said structure from outside corrosive forces, such as those listed above.
The various technological advances of corrosion mitigation, corrosion prevention, and pipeline monitoring have yielded incredible results when it comes to safeguarding the integrity of oil and gas pipelines. While a proper cathodic protection system is an important means of mitigating corrosion, it is just as important as carefully monitoring your pipeline’s integrity.
Now that you are aware of the dire importance of cathodic protection in the oil and gas industries, if you would like to learn any more about our corrosion testing services, including cathodic protection system design, and pipeline integrity testing, contact Dreiym today.