Types Of Corrosion Inhibitors

Zavenir Daubert as an Anti-corrosion specialist has various programs to prevent the attack of corrosion, one of which identifies the different types of corrosion inhibitors before providing any solution.

What Are Corrosion Inhibitors?

A corrosion inhibitor is a chemical solvent which is applied in a particular environment that significantly decreases the corrosion rate of elements (especially metals) exposed to that surrounding environment i.e. air and water.

CIs are considered the vanguard defense against corrosion.

Types Of Corrosion Inhibitors

  • Anodic Inhibitors
  • Cathodic Inhibitors
  • Mixed Inhibitors
  • Volatile Corrosion Inhibitors (VCI)

Anodic Inhibitors

Anodic inhibitors (CIs) operate very uniquely by creating a preventive oxide film on the exterior of the metal.

The reaction results in a large anodic shift that makes the metallic surface into the passivation area, which helps in the reduction of the possible corrosion of the material.

This whole procedure is sometimes called passivation.

Examples of anodic inhibitors include:

  • Chromate
  • Nitrite
  • Molybdate
  • Orthophosphate

Anodic Inhibitors are considered dangerous because of their chemical characteristics

Cathodic Inhibitors

Cathodic inhibitors work in two different methods:

  1. It may slow down the cathodic reaction itself Or,
  2. It may selectively be precipitating on cathodic regions to restrict the diffusion of eroding elements to the metal surface.

The cathodic reaction rate can be decreased by the use of cathodic poisons. But, It can also enhance the sensitivity of a metal to hydrogen induced cracking because during aqueous corrosion or cathodic charging the hydrogen can also be absorbed by the metal.

The use of oxygen scavengers that react with dissolved oxygen can also decrease the corrosion rates.

Example

  • Sulphite and bi-Sulphite ions that form Sulphates when reacting with Oxygen.
  • Catalyzed redox reaction by either Cobalt or Nickel.
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Mixed Inhibitors

These are film-forming compounds that reduce both the cathodic and anodic reactions. The most commonly used mixed inhibitors are silicates and phosphates used in domestic water softeners to prevent the formation of rust water.

Mixed Inhibitors are film-forming compounds that reduce both the cathodic and anodic reactions. The film-forming solution causes the formation of precipitates on the metal exterior preventing both anodic and cathodic sides indirectly.

Example

  • Silicates and phosphates used in residential water softeners to limit the development of rust water.
  • In aerated hot water systems, sodium silicate protects steel, copper and brass.

Volatile Corrosion Inhibitors

Volatile Corrosion Inhibitors (VCI), also called Vapor Phase Inhibitors (VPI), are products moved in a closed atmosphere to the section of corrosion by volatilization from a source. In boilers, volatile basic compounds, such as morpholine or hydrazine, are carried with vapor to stop corrosion in the condenser tubes by counterbalancing acidic carbon dioxide or by changing exterior pH towards less acidic and corrosive rates.

In closed confined spaces, such as shipping containers, VCI products such as VCI paper VCI bags or VCI rust removers are used. When these VC I come in contact with the metal surface, the vapor of these products is hydrolyzed by any moisture to release protective ions.

It is very important, for an efficient VCI, to produce inhibition quickly while lasting for a prolonged period.

Qualities of a VCI product depend on the volatility of its compounds; Quick action sequence high volatility while providing protection requires low volatility.

Example

In boilers, volatile mixtures such as morpholine or hydrazine, are carried with steam to stop corrosion in condenser pipes.

Only corrosion inhibitors professionals such as Zavenir Daubert can assess the efficiency of corrosion inhibitors that would be suitable for particular environments. Using these types of inhibitors should be part of corrosion prevention strategies of large-scale organizations.

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