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The Imidazoline and the imidazoline-quaternary ammonium corrosion inhibitors
2025-02-27
1. Properties of Imidazoline corrosion inhibitors used in the oil and gas
Imidazoline corrosion inhibitors are widely used in the oil and gas industry due to their unique properties that effectively combat corrosion in harsh environments. Here are the key features of these inhibitors:
1.Chemical Structure:
▶▶ Imidazolines are nitrogen-containing heterocyclic compounds with a 5-membered imidazoline ring (C₃N₂H₄). They typically include a long hydrocarbon chain and an alkyl amine substituent, which contribute to their functionality.
2.Adsorption on Metal Surfaces:
▶▶ The nitrogen atoms in the imidazoline structure allow for strong adsorption onto metal surfaces, particularly steel, due to the availability of lone pair electrons for bonding. This forms a protective film that acts as a barrier against corrosive agents.
3.Film Formation:
▶▶ They form a hydrophobic layer due to the hydrocarbon tail, which prevents moisture and corrosive chemicals from reaching the metal surface. This film can be either a single layer or multiple layers, enhancing the corrosion protection.
4.Low Toxicity and Environmental Friendliness:
▶▶ Compared to some other corrosion inhibitors, imidazolines are known for their relatively lower toxicity and environmental impact, making them more suitable for applications where environmental regulations are stringent.
5.Versatility:
▶▶ These inhibitors can be formulated to be oil-soluble, water-soluble, or dispersible in both phases, making them adaptable to various operational conditions like downhole applications, pipeline treatments, and storage tanks.
6.Efficiency in Acidic Environments:
▶▶ They are particularly effective in preventing acid corrosion, which is common in environments with CO₂ and H₂S gases, often found in oil and gas applications. Imidazolines can act as both anodic and cathodic inhibitors, providing mixed-type inhibition.
7.Stability and Durability:
▶▶ Imidazoline inhibitors are thermally stable, which is beneficial in high-temperature applications like those found in oil extraction and processing. They also have good resistance to the breakdown in water, maintaining their protective properties over time.
8.Synergistic Effects:
▶▶ When combined with other inhibitors like iodide ions or thiourea, their corrosion inhibition efficiency can be significantly enhanced due to synergistic effects. This can lead to better performance with lower concentrations of inhibitor.
9.Cost-Effectiveness:
▶▶ They offer a good balance between cost and performance, making them economically viable for large-scale industrial applications in the oil and gas sector.
10.Ease of Application:
▶▶ Imidazolines can be applied in batch or continuous treatment methods, offering flexibility in their use during different stages of oil and gas operations.
These features make imidazoline-based corrosion inhibitors a preferred choice for protecting infrastructure against corrosion in the oil and gas industry. However, the effectiveness can vary based on the specific formulation, concentration, and the conditions of the environment they are used in.
Ref web: https://en.wikipedia.org/wiki/Imidazoline
Ref web: https://chemistry.stackexchange.com/questions/76644/comparing-basicity-of-imidazole-and-2-imidazoline
Ref web:https://www.researchgate.net/figure/Sketch-of-adsorption-of-imidazoline-corrosion-inhibitor-on-corroding-Fe-surface_fig6_308721820
2. Compare the Imidazoline corrosion inhibitors and the imidazoline-quaternary ammonium salt corrosion inhibitor
A.Imidazoline corrosion inhibitors:
1. Chemical Structure:
Based on the imidazoline ring, typically with a long hydrocarbon chain for solubility and film-forming properties.
2. Mechanism:
Forms a protective film by adsorbing onto metal surfaces via nitrogen atoms, creating a hydrophobic barrier against corrosive agents.
3. Key Features:
Adsorption: Strong adsorption due to nitrogen's lone pair electrons.
Versatility: Effective in both aqueous and oily phases.
Stability: Good thermal and chemical stability.
Efficiency: Effective in acidic environments, especially against CO₂ and H₂S corrosion.
Environmental Impact: Generally considered less toxic.
4. Applications:
Used in pipelines, storage tanks, acidizing, and downhole applications.
5. Limitations:
Might require higher concentrations in very aggressive environments.
B. Imidazoline-quaternary ammonium salt corrosion inhibitors
1. Chemical Structure:
These are derivatives of imidazolines where an ammonium group is added, increasing the inhibitor's charge and potentially its interaction with metal surfaces.
2. Mechanism:
Besides film formation similar to imidazolines, the ammonium salt can enhance the ionic interaction with the metal surface, providing additional protection through electrostatic forces.
3. Key Features:
Enhanced Adsorption: The ammonium group can lead to stronger bonding with metal surfaces, potentially better in high salinity or high chloride environments.
Solubility: Often more soluble in water, which can be advantageous in water-based systems or when dealing with water cut in oil.
Synergistic Effects: Can interact better with other inhibitors or chemicals like sulfides, enhancing overall corrosion protection.
Improved Performance: Might offer superior protection in specific conditions where standard imidazolines are less effective.
4. Applications:
Particularly useful in environments with high water content, like produced water handling, or in systems where water corrosion is predominant.
5. Limitations:
Can be more sensitive to pH changes due to the ammonium component; performance might decrease in highly alkaline conditions.
Might have a slightly higher environmental impact due to the ammonium moiety.
C. Comparison Points:
Corrosion Inhibition Efficiency:
Both types are effective, but imidazoline-ammonium salts might provide better performance in specific scenarios like high salinity or in presence of chlorides.
Solubility:
Imidazoline-ammonium salts tend to have better water solubility, which can be crucial in water-wet systems.
Environmental and Safety Considerations:Imidazolines are generally seen as less toxic, but the ammonium salts might have different environmental profiles depending on their exact composition.
Cost and Application:
Imidazoline-ammonium salts might be more expensive due to additional synthesis steps, but their enhanced performance might justify the cost in critical applications.
Stability:
Both are stable under typical operating temperatures, but ammonium salts could be less stable in extreme pH conditions.
Versatility:
Imidazolines offer broad-spectrum use, while ammonium salts might be more tailored to specific applications where their unique properties are advantageous.
While standard imidazoline inhibitors serve well across a range of applications, imidazoline-ammonium-salt inhibitors might offer superior performance in environments with particular challenges like high water content or salinity, but with potentially increased costs and different environmental considerations. The choice between them would depend on the specific operational conditions, economic considerations, and environmental policies of the oil and gas operations.
D. Several types of corrosion inhibitors exhibit improved inhibition rates as temperature increases. Here are some notable examples:
1.Quaternary Ammonium Compounds (QACs):
Mechanism: These compounds often form stable, protective films on metal surfaces which become more effective at higher temperatures due to enhanced adsorption or changes in the inhibitor's solubility.
Examples: Benzalkonium chloride or cetyltrimethylammonium bromide. They can show better performance at elevated temperatures due to increased interaction with metal surfaces.
2.Phosphate Esters:
Mechanism: They can form iron phosphate complexes that become more stable and protective at higher temperatures, enhancing passivation.
Examples: Trisodium phosphate or polyphosphate esters. Their effectiveness can increase with temperature as they form denser protective layers.
3.Thiourea Derivatives:
Mechanism: Thiourea compounds can chelate with metal ions, forming protective layers. At higher temperatures, their adsorption might increase, leading to enhanced inhibition.
Examples: Thiourea itself or its derivatives like allyl thiourea, which can show improved performance due to better film formation.
4.Sulfonates and Sulfides:
Mechanism: These inhibitors can form stable films that might become more robust at elevated temperatures. Sulfides, in particular, can form protective layers with metals like iron.
Examples: Sodium sulfonate or alkyl benzene sulfonate; their inhibition efficiency can increase as they form more effective barriers against corrosive agents at higher temperatures.
5.Imidazolines with Special Additives:
While standard imidazolines might lose efficiency at very high temperatures, certain formulations with additives like iodides or thiocyanates can enhance performance.
Examples: Some imidazoline inhibitors combined with potassium iodide or sodium thiocyanate can show better inhibition as these additives synergistically improve film stability at high temperatures.
6.Silanes:
Mechanism: Silane-based inhibitors can polymerize on metal surfaces, creating a protective coating. High temperatures can accelerate curing and bonding, improving the barrier properties.
Examples: Amino or mercapto silanes which can form siloxane networks that are more effective at higher temperatures.
7.Amines and Amine Salts:
Mechanism: These can form complexes or films with metal ions that are more protective at elevated temperatures, especially in acidic environments.
Examples: Cyclohexylamine or morpholine salts, where the amine component can react more effectively with metal surfaces at increased temperatures.
8.Polymeric Inhibitors:
Mechanism: Polymers can form thick, stable films on metal surfaces, which at higher temperatures, can cross-link or adhere better, providing superior protection.
Examples: Polyvinylpyrrolidone or polyacrylamide derivatives might have enhanced performance as the polymer chains interact more effectively with the metal.
When using these inhibitors, it's important to consider:
Compatibility: Ensure the inhibitor is compatible with other chemicals in the system.
Concentration: Adjustments might be needed at higher temperatures for optimal performance.
Specific Conditions: The exact improvement in inhibition rate depends on the nature of the corrosive environment, including pH, pressure, and the presence of specific gases or salts.
Testing under operational conditions is often necessary to confirm the enhanced performance of these inhibitors at higher temperatures.
Casing and tubing for oil and gas wells are frequently made of steel alloys. Many corrosive gases, organic acids, salts, and other contaminants are present in the fluids of oil and gas wells, which hurt their productivity, efficiency, and continuous production. The common corrosive species include carbon dioxide (CO2), hydrogen sulfide (H2S), water (H2O), organic acids (HCOOH, CH3COOH etc.) and salts (NaCl, CaCl2, MgCl2, NH4Cl etc.) that can cause the corrosion of metals at any stage of production, purification, storage and transportation processes.
Acidizing corrosion inhibitors must be able to mitigate corrosion in both low carbon alloy steels and high chrome steels, be stable in high acid concentrations and under high reservoir temperatures. YOUZHU’s range of corrosion inhibitors, exhibits excellent inhibition on various metal types, under different temperature and in varying acid concentrations. Additionally, in less severe conditions (e.g. lower acid concentration and/or lower temperatures) the CIs（Corossion Inhibitors） can also be added directly to corrosive treating fluids to protect equipment.
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