Chemical Additives

Corrosion Inhibitors

1. Definition & Mechanism

Corrosion inhibitors are chemical compounds that minimize or prevent metal degradation in corrosive environments by:

• Forming a protective film (adsorptive or passivating layer) on metal surfaces
• Blocking electrochemical reactions (anodic/cathodic inhibition)
• Scavenging corrosive agents (e.g., oxygen, H₂S)

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2. Key Applications by Industry

Industry	Protected Components	Common Inhibitor Types
Oil & Gas	Pipelines, storage tanks	Imidazolines, phosphate esters
Automotive	Cooling systems, fuel tanks	Nitrites, silicates
Aerospace	Aircraft alloys	Chromates (restricted), organic azoles
Marine	Ship hulls, offshore platforms	Volatile amines (VCI), molybdates
Water Treatment	Boilers, heat exchangers	Polyphosphates, filming amines

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3. Classification by Function

Type	Mechanism	Example Compounds
Anodic	Blocks oxidation (metal dissolution)	Sodium chromate, nitrites
Cathodic	Prevents reduction (H⁺/O₂ consumption)	Zinc salts, polyphosphates
Mixed	Dual-action protection	Benzotriazole (for copper)
Volatile (VCI)	Vapor-phase protection	Cyclohexylamine nitrite

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4. Technical Specifications

Property	Typical Value/Requirement
Dosage	50–500 ppm (varies by system)
pH Range	6–10 (depends on inhibitor type)
Temperature Stability	Up to 150°C (for oilfield chemicals)
Efficiency	>90% corrosion reduction

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5. Environmental & Safety Considerations

• Regulatory Compliance:
  • Restricted: Chromates (RoHS/REACH-regulated)
  • Eco-Friendly: Bio-based inhibitors (e.g., plant extracts)
• Handling:
  • Use PPE (gloves, goggles) for concentrated formulations
  • Biodegradability: OECD 301B testing for water-soluble types