Corrosion refers to the tendency of metals to return to their natural condition and the deterioration of material due to chemical and electrochemical reactions. Pipeline metals corrode when exposed to certain elements or materials. This is a natural process which can be halted if the conditions are changed or treatment is applied. If, however, there is no change in conditions or no treatment applied, the metal will continue to corrode until it disintegrates. So what are the main elements that impact pipeline corrosion?
1. High temperatures
High temperatures can cause corrosion in pipelines due to the increased temperature of the metal. If the metal is in contact with heat that contains oxygen or compounds chemicals such as sulfur, the metal will begin to oxidize. There is, however, a plus side. Oxidization can help protect many metals by providing a naturally protective layer, which prevents a further atmospheric attack on the surface. So some oxidization such as the green patina seen on bronze can be beneficial for the longevity of the metal.
2. A high-carbon environment
This causes metal dusting and occurs when metals are exposed to high carbon environments, such as synthesis gas. These gasses and high-CO environments wear away at the pipeline metals, causing them to break down into a powdery substance. Metal dusting is one of the most significant forms of pipeline corrosion.
Microbiologically-influenced corrosion (MIC) occurs when metal is attacked by microorganisms which eat away at the metal, usually in localized areas. These organisms (usually chemoautotrophs) produce hydrogen sulfide which can cause the metal to oxidize and crack. MIC is most commonly found on metal which is immersed in sea water.
4. Atmospheric air
This leads to crevice corrosion to pipelines, a localized corrosion which occurs in areas where the metal has little access to air. Areas such as metal seams and between parts and spaces become filled with deposits and begin to eat away at the metal.
5. Low oxygen concentration
Low levels of oxygen or high levels of chloride can interfere with the structure of pipelines. The metal, when under attack, will show signs of localized erosion in the form of pitting. If not treated, the erosion will continue. Pitting corrosion is one of the most common forms of metal corrosion damage.
Impurities such as impure gas, solids, or liquids can wear pipelines down. Though plenty of contaminated gasses do not damage metal in dry form, they can form harmful corrosive droplets if exposed to moisture. An example of such impure agents is hydrogen sulfide.
Pipeline Corrosion Protection
Pipelines can be treated to help prevent or halt corrosion from happening or advancing. There are many innovative corrosion management treatments around to stop corrosion from damaging the metal material. Some metals are naturally resistant to corrosion, such as stainless steel. However, most metals can incur erosion problems. In some cases, corrosion is removed using a chemical process. In other cases, it is removed by removing some of the surface metal. The best way, however, to deal with pipeline metal erosion is to treat the metal in the first place before erosion occurs.
There are many surface treatments and applied coatings that can be used on metal to help protect it from erosion. These treatments and coatings provide a barrier between damaging environmental factors and the metal structure. Most metals today are coated with a surface treatment to help preserve the metal, and then re-coated again at intervals over the years. Alternatively, some metals are painted to protect the surface. Painted metal coatings are easy to apply and provide an anti-corrosive protective seal on the surface.
Coatings will differ on the kind of metal involved along with the kind of corrosion being prevented. For instance, coatings made from aluminum and zinc are beneficial for preventing galvanic corrosion in steel alloys and iron. Large components like energy windmills and bridges can also benefit from these coatings. On the other hand, a thin layer of cadmium can be helpful for iron and steel fasteners and bolts.
If you notice any metal material or the pipeline metal under attack from these elements and rectification is difficult, you can call up a corrosion consultancy company to have a corrosion inspection carried out.