Primer | Meaning and Functions of the Primer

Meaning of Primer

Primer is the main preparatory coat applied on steel, wood or canvas to prevent corrosion or to provide a key for subsequent coat. In other words, it is designed to adhere to surfaces and to form a binding layer that is better prepared to receive the paint.

Some Basic Primers

Etch primers

Zinc epoxy primers

Inorganic Zinc Ethyl Silicate Primer (Minimum 85% Zinc dust by weight in the dried film)

Epoxy  Red Oxide Zinc Phosphate Primer

Self priming surface tolerant Epoxy Mastic paint

Amine Adduct Cured Epoxy Holding Primer

Two Component Polyamide cured Epoxy Primer

The Functions of Primer

The protective paint systems usually consist of primer, undercoat(s) and finish coats. Each coating ‘layer’ in any protective system has a specific function, and the different types are applied in a particular sequence of primer followed by intermediate / build coats in the shop, and finally the finish or top coat either in the shop or on site.

  • The primer is applied directly on cleaned or blasted steel surfaces immediately to prevent dis-colorization or reformation of rust.
  • It is a key part to any professional painting or coating. It is a preparatory coating which should be applied to steel surface prior to any painting activity.
  • A primer will not work as designed anywhere else other than in contact with the substrate. A primer, normally low volume solid materials, wets out the substrate and provides excellent adhesion and also provides a key for any subsequent layer.
  • The binders usually have a relatively low resistance to vapour transmission, and allow water into the film to carry tiny amounts of the rust inhibitive pigmentation onto the substrate to form a passivating layer.
  • Other primers exist for non-ferrous substrates such as Wash or Mordant primers, and PVB etch primers.  Mordant means of a corrosive nature, or will bite into, and as suggested contains an acid, phosphoric acid. Their use is limited nowadays
  • Their primary use was for etching new galvanizing. The reaction turns the surface black (zinc phosphate salts).

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