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Essential to coating is a properly executed pretreatment, as it promotes adhesion.  Various techniques are applied depending on the final layer.

 

Mechanical pretreatment

Steel is blasted under great pressure with steel shot, resulting in a pure (SA 2 1 / 2) and very rough surface. This rough surface ensures the adhesion of the coating. For thin coatings such as  Teflon® , we work with a fine, inert abrasive.

If  Rilsan®  is to be used in a more aggressive environment, we apply an additional primer.

 

 

Chemical pretreatment

In the pretreatment tunnel, the pieces are degreased, treated with zinc phosphate, passivated and rinsed with demineralized water. This results in a zincphosphate trication layer that is anticorrosive and promotes adhesion.

The pictures below illustrate the deterioration of a coated part after a saltspray test of 1,000 hours.

The parts had the following pretreatments:

  1. Only degreasing
  2. Treatment with iron phosphate
  3. Treatment with zinc phosphate(our quality)
  4. Microscopic photo of the crystalline zinc phosphate

 

Metal spraying

A flame gun is used to spray zinc wires on to the treated pieces. This results in a 40 to 80 μ thick protective zinc layer upon which a coating is then applied.