- Objectives of Exterior Varnishing:
- Provide protection against corrosion.
- To give a good appearance to the exterior, with decorative and product identification function.
- Be resistant to sterilization processes.
- Facilitate and be resistant to mechanization processes.
- Abrasion resistant.
- Types of Varnishes:
- Vinyl, Acrylic or Epoxy-Phenolic: These exterior coatings are applied to protect tinplate from external corrosion. They can be colorless or, in some cases, gold-plated.
- Finishing Varnish: It is a transparent varnish applied over the printing to protect it, since the inks have little resistance to abrasion.
- Application Process:
- Varnishing table: The required weight of varnish is applied and the varnished sheets are placed on grills that guide them through an oven to cure the varnish.
- Curing Oven: The sheets pass through an oven where the varnish is cured, ensuring that the applied coating is durable and resistant.
- Exterior coating:
- To protect the outer weld and preserve the integrity of the can, a protective varnish is applied to the side seam. This varnish is usually colorless and fast drying.
- Quality Control:
- Tests are carried out to control the quality of varnish application, ensuring that the protection and appearance objectives are met.
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