How long a Corrosion Inhibitor may be Used to Avoid Corrosion in a Pipe
The duration for which a corrosion inhibitor is used in a pipe depends on several factors, including the type of pipeline, the fluid being transported, the environmental conditions, the inhibitor’s chemical properties, and the application method.
Corrosion inhibitors are chemical compounds injected or applied to pipelines to reduce corrosion by forming a protective film on the pipe’s inner surface, neutralizing corrosive agents, or altering the environment.
Overview of Corrosion Inhibitor Types
• Film-Forming Inhibitors: These inhibitors adsorb onto the metal surface, forming a protective barrier (film) that prevents corrosive agents (e.g., water, chloride ions, CO₂) from reaching the metal.
They can act via physical adsorption (electrostatic attraction) or chemisorption (chemical bonding) and are often classified as anodic, cathodic, or mixed-type inhibitors based on their effect on electrochemical reactions.
Organic compounds with heteroatoms (O, N, S) or polar groups are typical film-forming inhibitors.
• Scavenger Inhibitors: These reduce corrosivity by neutralizing or removing aggressive substances (e.g., oxygen, H₂S, CO₂) from the environment. Scavengers do not primarily form a film but instead chemically react with corrosive species to mitigate their impact. Examples include oxygen scavengers (e.g., sulfites) or H₂S scavengers.
• Other Types: These include volatile corrosion inhibitors (VCIs) for vapor-phase protection, passivating inhibitors (e.g., chromates that promote oxide layer formation), or hybrid inhibitors combining multiple mechanisms.
Role of Corrosion Inhibitors in Pipelines
Corrosion inhibitors are used in pipelines (e.g., oil, gas, water, or chemical transport) to protect the internal metal surface from corrosion caused by corrosive fluids (e.g., water, CO₂, H₂S, or acids).
They are typically applied in:
• Continuous injection: To maintain ongoing protection during pipeline operation.
• Batch treatment: Periodic application to replenish the protective film.
• Cleaning or maintenance operations: As part of pigging or flushing to address corrosion alongside other issues.
Unlike drag-reducing agents (DRAs), which primarily enhance flow efficiency, corrosion inhibitors directly mitigate material degradation, extending pipeline life.
Duration of Corrosion Inhibitor Use
The “duration” of corrosion inhibitor use can refer to either the timeframe of active application (e.g., how long it is injected or applied) or the effective lifespan of the inhibitor’s protective effect before reapplication is needed. Here’s a breakdown:
1. Continuous Injection
◦ Duration: In many oil and gas pipelines, corrosion inhibitors are injected continuously at low concentrations (e.g., 5–100 ppm, depending on the system) to maintain a protective film during operation. This can last for months to years, as long as the pipeline is in service and the inhibitor is regularly supplied.
◦ Example: In offshore oil pipelines, inhibitors are often injected continuously to counter corrosion from seawater or produced water. This is common in systems described in and, where inhibitors are part of daily operations.
◦ Replenishment: The inhibitor’s effectiveness may diminish due to dilution, degradation, or consumption by corrosive agents, requiring ongoing injection. Monitoring systems (e.g., corrosion coupons or probes) determine if adjustments are needed.
2. Batch Treatment
◦ Duration: Batch treatments involve applying a higher concentration of inhibitor (e.g., 1–10% solution) periodically, typically every few weeks to months, depending on the corrosion rate and inhibitor persistence. Each batch application may take hours to days, depending on pipeline length and flow conditions.
◦ Example: In gas pipelines, batch inhibitors are applied between pigging runs, forming a film that lasts 4–12 weeks. For a 150 km pipeline, a batch treatment might involve injecting inhibitor for 6–24 hours, with the protective effect lasting weeks to months.
◦ Factors: The frequency of batch treatments depends on the corrosivity of the fluid (e.g., high H₂S content requires more frequent application) and the inhibitor’s film-forming ability.
3. Effective Lifespan of Inhibitor
◦ Protective Film Duration: Once applied, the inhibitor forms a protective film that can last from days to months, depending on:
▪ Inhibitor Type: Film-forming inhibitors (e.g., amines, imidazolines) create persistent barriers, lasting weeks to months,. Scavengers (e.g., oxygen scavengers) neutralize corrosive agents but may need frequent reapplication (hours to days).
▪ Environmental Conditions: High temperatures, pressures, or flow rates can erode the film faster, reducing its lifespan. For example, in high-velocity pipelines, shear forces may strip the film, requiring reapplication every few weeks.
▪ Fluid Chemistry: High water cut, low pH, or presence of CO₂/H₂S shortens the film’s life, as seen in sour gas pipelines.
◦ Field Data: Studies show that organic film-forming inhibitors in oil pipelines can maintain protection for 30–90 days under moderate conditions, while harsher environments (e.g., high CO₂) may require reapplication every 1–4 weeks.
4. Application During Cleaning or Maintenance
◦ Duration: When used as part of pigging or chemical cleaning, inhibitors are applied for the duration of the operation, typically hours to a day. For example, during pipeline pigging, inhibitors may be injected alongside cleaning agents to protect the freshly exposed metal surface.
◦ Example: A 300 mm diameter, 100 km pipeline might require inhibitor injection for 6–12 hours during a pigging run, with the protective effect lasting weeks until the next maintenance cycle.
5. Specific Inhibitor Types and Performance
◦ Organic Inhibitors (e.g., amines, quaternary ammonium compounds): These form durable films, lasting weeks to months, but may degrade under high temperatures (>100°C-150°C), requiring more frequent application.
◦ Inorganic Inhibitors (e.g., chromates, phosphates): Less common in pipelines due to environmental concerns, but their effect may last days to weeks, depending on solubility and fluid chemistry.
◦ Volatile Corrosion Inhibitors (VCIs): Used in gas pipelines or during shutdowns, VCIs can protect for months in low-flow or static conditions by vaporizing and coating the pipe surface.
◦ Novel Formulations: Recent advancements (e.g., water-dispersible inhibitors, green chemicals or graphene-based inhibitors) show extended lifespans, with some maintaining protection for up to 6 months in lab tests under mild conditions.
Factors Affecting Duration
• Pipeline Material: Carbon steel pipelines corrode faster than stainless steel, requiring more frequent inhibitor use. For example, carbon steel in sour service (H₂S-rich) may need weekly batch treatments,.
• Fluid Composition: High water content, CO₂, H₂S, or chlorides increase corrosivity, shortening the inhibitor’s effective lifespan. For instance, produced water with 5% H₂S may require reapplication every 1–2 weeks.
• Temperature and Pressure: Higher temperatures accelerate corrosion and inhibitor degradation, reducing film persistence. For example, at 80°C, an inhibitor’s film may last half as long as at 20°C.
• Flow Conditions: Turbulent flow or high shear rates can strip the inhibitor film, necessitating more frequent application. In high-velocity pipelines (e.g., >2 m/s), inhibitors may need reapplication every few days to weeks.
• Inhibitor Concentration: Higher concentrations (e.g., 100 ppm vs. 10 ppm) often extend protection but increase costs. Optimal dosing is determined through corrosion monitoring,.
• Application Method: Continuous injection maintains steady protection, while batch treatments are less consistent but more cost-effective for low-corrosion systems.
Typical Duration Estimates
Based on industry practices and available data:
• Continuous Injection: Ongoing for the pipeline’s operational life (months to years), with inhibitor levels maintained at 5–100 ppm. Replenishment occurs as needed based on monitoring.
• Batch Treatment: Applied for hours to days every 2–12 weeks, with the protective film lasting days to months. For example, a 150 km oil pipeline might receive a 12-hour batch treatment every 4 weeks.
• Cleaning Operations: Inhibitors are injected for hours (e.g., 6–24 hours during pigging), with protection lasting weeks until the next cycle.
• Film Lifespan: Under typical conditions (e.g., crude oil pipeline, 20–60°C, moderate corrosivity), a film-forming inhibitor lasts 30–90 days. In harsh conditions (e.g., high H₂S, high temperature), it may last 1–4 weeks.
Practical Considerations
• Monitoring: Corrosion rates are tracked using coupons, probes, or non-destructive testing (e.g., ultrasonic inspection) to determine reapplication frequency. For example, a corrosion rate of <0.1 mm/year may allow less frequent batch treatments,.
• Optimization: Software tools like Seeq or Simcenter Flomaster can model corrosion rates and optimize inhibitor dosing schedules.
• Environmental Regulations: Some inhibitors (e.g., chromates) are restricted due to toxicity, favoring eco-friendly alternatives like organic or bio-based inhibitors, which may have shorter lifespans but are safer.
• Cost: Continuous injection is costlier than batch treatments, so operators balance inhibitor cost against corrosion damage costs. For example, a 1% batch treatment every 6 weeks may be more economical than 20 ppm continuous injection.
Comparison to Drag-Reducing Agents
Unlike DRAs, which are used to reduce turbulence and indirectly aid pipe maintenance, corrosion inhibitors directly protect the pipe material.
DRAs are typically injected continuously or intermittently for flow enhancement, with effects lasting hours to days due to shear degradation.
Corrosion inhibitors, however, form persistent films, with protective effects lasting weeks to months, making their application less frequent in batch mode but potentially more consistent in continuous mode.
Final Comments
The duration of corrosion inhibitor use in a pipe varies by application:
• Continuous injection: Ongoing for months to years at low concentrations (5–100 ppm), with constant replenishment.
• Batch treatment: Applied for hours to days every 2–12 weeks, with the protective film lasting days to months (typically 30–90 days under moderate conditions, 1–4 weeks in harsh environments).
• Cleaning operations: Injected for hours (e.g., 6–24 hours during pigging), with protection lasting weeks.
• Effective lifespan: Film-forming inhibitors last weeks to months, while scavengers may require reapplication every hours to days.
The exact duration depends on pipeline material, fluid chemistry, temperature, flow conditions, and inhibitor type.
NOCORGREEN™ solution
NOCORGREEN™ is a film-forming inhibitor, which is influenced by its composition (primarily aloe barbadensis miller and aloe chinensis compounds).
NOCORGREEN™ is described as a “green and eco-friendly product” made from natural plant polysaccharides, primarily from Aloe barbadensis miller and Aloe chinensis, used as a corrosion inhibitor in industries like oil and gas, water treatment, and desalination.
Composition and Properties
• Aloe-Based Compounds: NOCORGREEN™ contains polysaccharides, enzymes, amino acids, and anthraquinones derived from aloe. Studies on aloe extracts (e.g., Aloe vera) as corrosion inhibitors highlight the presence of:
◦ Polysaccharides: Such as mannose and galactose, which have oxygen-containing functional groups (e.g., hydroxyl groups) that can adsorb onto metal surfaces.
◦ Anthraquinones: Compounds like aloin, which contain polar groups (e.g., carbonyls, hydroxyls) capable of forming complexes with metal ions or adsorbing onto surfaces.
◦ Antioxidants: Aloe is rich in antioxidants, which can neutralize reactive species, potentially contributing to scavenger-like behavior.
• Functional Groups: Research on aloe extracts (e.g.,) identifies heteroatoms (O, N) and polar groups that facilitate adsorption on metal surfaces via physisorption (electrostatic) or chemisorption (coordinate bonding). FT-IR and LCMS analyses confirm these groups, which are critical for film-forming inhibition.
Mechanism of Action
Different materials and related studies (that you can find on this site) provide clues about NOCORGREEN™’s mechanism:
• Film-Forming Evidence:
◦ Studies on Aloe vera extracts (e.g.,) demonstrate that aloe acts as a corrosion inhibitor by adsorbing onto metal surfaces (e.g., API 5L steel in seawater or mild steel in HCl), forming a protective film. The adsorption follows the Langmuir isotherm, indicating a monomolecular layer, typical of film-forming inhibitors.
◦ Inhibition efficiency increases with concentration (e.g., 83.75% at 300 mg/L in seawater), suggesting that more inhibitor molecules adsorb to cover the metal surface, a hallmark of film-forming behavior.
◦ Electrochemical tests (e.g., Tafel polarization, EIS) show that aloe extracts act as mixed-type inhibitors, affecting both anodic (metal dissolution) and cathodic (e.g., oxygen reduction) reactions, which is consistent with film-forming inhibitors that block active sites on the metal surface.
◦ Surface analyses (SEM, AFM, EDS) confirm a smoother metal surface with aloe extract, indicating a protective film that reduces corrosion product formation.
◦ For NOCORGREEN™, Aloetrade claims it “protects tanks, pipelines, boilers, heat exchangers, cooling towers, valves, and equipment from corrosion,” implying a barrier effect, likely via film formation, as polysaccharides and anthraquinones can adsorb onto metal surfaces.
• Scavenger Evidence:
◦ Aloe’s antioxidant properties, noted in, suggest it could neutralize reactive species (e.g., oxygen or free radicals) that contribute to corrosion, resembling scavenger behavior. Antioxidants in aloe may form complexes with corrosive agents, reducing their availability.
◦ However, there’s no direct evidence from Aloetrade’s materials or studies that NOCORGREEN™ primarily works by scavenging specific corrosive species like O₂ or H₂S. Scavenger inhibitors typically target well-defined corrosive agents, but NOCORGREEN™’s description emphasizes surface protection rather than environmental modification.
◦ Some aloe-based inhibitors in acidic media (e.g., 15% HCl in) show scavenger-like activity by complexing with metal ions (e.g., Fe²⁺), but this is secondary to film formation.
• Other Mechanisms:
◦ Volatile Corrosion Inhibitors (VCIs): There’s no indication that NOCORGREEN™ is used in vapor phase, as it’s applied in liquid systems (e.g., fracking fluids, water treatment). VCIs are typically used in closed environments, unlike NOCORGREEN™’s applications.
◦ Passivating Inhibitors: These promote oxide layer formation (e.g., chromates), but aloe-based inhibitors lack this mechanism, relying instead on organic adsorption.
◦ Hybrid Behavior: Aloe extracts are described as mixed inhibitors with both physisorption and chemisorption, potentially combining film-forming and minor scavenger effects. NOCORGREEN™ may exhibit hybrid behavior, but film formation appears dominant.
Specific Claims for NOCORGREEN™
• Applications: NOCORGREEN™ is used in oil and gas (e.g., fracking, wells), water treatment, and desalination, protecting pipelines and equipment. In fracking, it’s an alternative to formic acid and acetaldehyde, suggesting it targets corrosion in acidic or saline environments, likely via surface adsorption.
• Environmental Friendliness: Its biodegradable, plant-based nature aligns with green inhibitors, which are often film-forming due to their organic composition (e.g., polysaccharides, amino acids).
• Comparison to Other Products: Aloetrade’s STOPSCALE™ (a scale inhibitor) explicitly mentions forming a protective film against carbonate/sulfate scale, suggesting that their aloe-based products, including NOCORGREEN™, may share similar film-forming mechanisms for corrosion protection.
Categorization of NOCORGREEN™
Based on the evidence:
• Film-Forming Inhibitor: The primary mechanism of NOCORGREEN™ is likely film-forming, as:
◦ Its aloe-based composition (polysaccharides, anthraquinones) contains polar groups that adsorb onto metal surfaces, forming a protective barrier, as seen in studies of Aloe vera extracts.
◦ Electrochemical studies of aloe inhibitors show mixed-type inhibition via adsorption, consistent with film-forming behavior.
◦ Aloetrade’s claims emphasize protection of metal surfaces (pipelines, tanks), implying a barrier effect.
◦ The Langmuir adsorption isotherm observed in aloe studies supports a monomolecular film, typical of interface inhibitors.
• Scavenger Inhibitor: While aloe’s antioxidants could theoretically scavenge reactive species, there’s insufficient evidence that NOCORGREEN™ primarily works this way. Scavenger activity (e.g., complexing Fe²⁺ or neutralizing oxygen) may be a secondary effect, but film formation is the dominant mechanism.
• Other Types: NOCORGREEN™ does not fit as a VCI (no vapor-phase use) or passivating inhibitor (no oxide layer promotion). Its hybrid nature (film-forming with minor scavenger effects) is possible, but it’s best classified as a film-forming inhibitor.
Conclusion
NOCORGREEN™, manufactured by Aloetrade America LLC, is categorized as a film-forming corrosion inhibitor. Its aloe-based composition, rich in polysaccharides and anthraquinones, adsorbs onto metal surfaces to form a protective film, reducing corrosion in environments like oil and gas pipelines, water treatment systems, and desalination plants.
This is supported by studies on Aloe vera extracts showing adsorption-driven inhibition and Aloetrade’s claims of surface protection. While minor scavenger effects are possible due to aloe’s antioxidants, film formation is the primary mechanism.
If you require additional details about NOCORGREEN™’s application or specific performance data, please visit the specific product page or contact to us.