Corrosion is the process in which a refined metal reacts with its environment, resulting in a gradual degradation and destruction of the original metal substrate.
An everyday example of corrosion exists on the rusty gears of a bicycle that has been left outside. Rust, which is the most familiar example of corrosion, is a consequence of iron metal components reacting with environmental oxygen in the presence of water. This form of corrosion produces a variety of iron oxides that have a negative impact on the structural integrity of the non-corroded metallic shape (i.e. new gears work better than rusty ones).
Corrosion in Pipelines for Oil and Gas
While a rusty bicycle produces a squeaky bike-ride, corrosion in an oil-field pipeline can result in a more dangerous and costly outcome. Stakeholders take many precautions to nullify or limit the amount of corrosion in the oil and gas industry that are associated with the potential of an oil spill or gas leak. Corrosion is a serious threat to not only the assets of the oil and gas industry, but to the environment in which we all live.
While rust is the product of iron’s reaction with oxygen in the presence of water, the oil and gas industry encounter a much larger list of environmental factors that serve as serious threats to corrosion. Corrosion in the oil and gas industry, specifically in the case of oil wells and tubulars, occurs due to factors such as temperature, the presence of carbon dioxide (CO2), hydrogen sulfide (H2S), electrolytes (such as those found in brine) and flow conditions. The major forms of oil-field related corrosion includes sweet (CO2 corrosion), sour (H2S corrosion), oxygen, galvanic, crevice, erosion, and microbiologically induced corrosion (MIC) as well as stress corrosion cracking.
To prevent such factors, as those mentioned above, from corroding wells and tubulars, the oil-and-gas industry utilizes common methods such as (1) cathodic protection, (2) applied coatings, and (3) the use of corrosion inhibitors to combat corrosion.
An example of cathodic protection can be observed upon applying a zinc rich coating to the surface of steel pipes. In this case, zinc is considered a “sacrificial metal” and will corrode before the protected metallic substrate. Additionally, applied coatings, such as primers, epoxy/polyurethanes, and paints containing anti-corrosive pigments can be applied to metallic surfaces to aid as a barrier between the metal and the corrosive environment, thus slowing down the rate of corrosion.
Though cathodic protection and applied coatings are useful methods to mitigate corrosion, the use of corrosion inhibitors is one of the most efficient and economically feasible methods for the oil-and-gas industry. Corrosion inhibitors are broadly classified as anodic, cathodic, or mixed corrosion inhibitors. Such corrosion inhibitors can be organic or inorganic in nature.
Some common inorganic corrosion inhibitors include chromium, molybdenum, zinc, phosphates, sodium sulfite and hydrazine. Organic corrosion inhibitors, based on a broad range of chemical compounds, including amines, aromatics, heterocyclics, carboxylic acids, sulfur and nitrogen-containing moieties, can also be incorporated into a coating to improve the corrosion resistance. These corrosion inhibitors function by passivating either the anode or cathode on the metal substrate or by creating a protective film on the metal surface thereby preventing corrosive components from encountering the metal substrate.
The most widely used corrosion inhibitors in the oil-and-gas industry are nitrogen-based surfactants. The surfactants in paint are effective corrosion inhibitors for oil and gas production due to their lipophilic and hydrophilic nature. Painting and coating surfactants work by partitioning between the oil and water phase scavenging corrosive species or adsorbing to the surface of the metal producing a protective film (Figure 1). Such film forming corrosion inhibitors consists of fatty amines/diamines, alkoxylated fatty amines/diamines, imidazolines, amides and quaternary ammonium compounds.1
The selection of the most effective corrosion inhibitor must take each of the factors, such as temperature, the presence of carbon dioxide (CO2), hydrogen sulfide (H2S), flow conditions, and electrolytes into consideration in order to optimize performance and increase safety.
In order to help service providers to overcome this difficulty, Oxiteno has developed the ULTROIL® CI line of corrosion inhibitor intermediates (Figure 2). This line provides corrosion protection on internal surfaces, maintaining the integrity of the metallic materials in the transport and storage of hydrocarbons as well as reducing health and environmental hazards. Oxiteno’s line of ULTROIL® CI corrosion inhibitor intermediates are specially designed to be suitable for sweet (CO2) and sour (H2S) corrosion, to bear excellent film-forming properties, and to exhibit high electrolyte tolerance. Furthermore, this line of corrosion inhibitors contains a high active content (>98%) thereby making them efficient even at low dosages.
As one of the top US surfactant manufacturers, Oxiteno aims to develop sustainable and innovative solutions to meet the technological challenges of the oil-and-gas industry. We take a market-oriented approach, working closely with service providers to develop cleaner and more efficient solutions for the oil-and-gas production chain.
Oxiteno’s expertise in ethoxylation and the new production facility located in Pasadena, TX, positions our team to become a leading provider of corrosion inhibitor intermediates to the oil-and-gas industry. For more information regarding Oxiteno’s capabilities please contact us today!
Dariva, C.g., et al. “Corrosion Inhibitors – Principles, Mechanisms and Applications. Intech., 1(16), 365-379