Passivator

Definition - What does Passivator mean?

A passivator is a type of corrosion inhibitor that appreciably changes the potential of a metal to a more noble (positive) value. It is a substance (e.g., chromate) that passivates, especially by forming a protective film on a metal.

Oxidizing agents are the most common passivators, although other substances may also be used for passivation.

Passivators can be used after:

  • Pickling
  • Mechanical treatments such as:
    • Grinding
    • Brushing
    • Blasting
  • Removal of discolorations during pickling
  • Removal of free iron
  • Reducing the formation of toxic nitric fumes during pickling

Corrosionpedia explains Passivator

A passivator can be an acidic, liquid passivating chemical used in either an immersion or spray final rinse to improve paint adhesion and minimize corrosion such as under-film corrosion and blistering. For instance, nitric acid is used to passivate aluminum and chromate solutions to passivate zinc coatings. Since passivation is primarily determined by metallurgical and environmental factors, the rate of corrosion is reduced by passivation depending on the type of metal and its environment.

Passivators are extremely useful in mitigating corrosion damage, however even a high-quality alloy corrodes if its ability to form a passivating film is hindered. Proper selection of the right grade of material for the specific environment is important for the long-lasting performance of this group of materials. If breakdown occurs in the passive film due to chemical or mechanical factors, the resulting major modes of corrosion may include:

  • Pitting corrosion
  • Crevice corrosion
  • Stress corrosion cracking (SCC)

Passivators' working mechanisms are similar to passivation. For example, surface corrosion can occur when wet surfaces react with atmospheric oxygen. The formation of flash rust can be eliminated with the use of surface passivators, which chemically change the active surface of metal to a much less reactive state. It does not leave a film or residue to interfere with coating adhesion. It also removes soluble salts as it passivates, and is an effective alternative to hazardous chemical rust inhibitors.

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