Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers


Spot Priming

Last updated: August 31, 2017

What Does Spot Priming Mean?

Spot priming is the process of applying a primer to particular regions of a substrate that need it. This technique is applicable before any interior and exterior painting on wall, metal and wood surfaces, and is often done when repainting a substrate.

Primer paint is applicable to certain parts which need repair because of stains, cracks and pores. Since the top coat can adhere to old coats, after applying spot priming the entire wall or surface can be uniformly painted. It is used to protect the substrate from moisture and also to prevent stain or rust bleed through after painting. In metals, it can be an anti-corrosion coating that acts similarly to a sealant or gasket.


Corrosionpedia Explains Spot Priming

Spot priming is accomplished by using either oil or latex primers, depending on the substrate. The primers contain resins and pigments which adhere to the substrate, thus providing bonding that is essential to allow the top coat to stick and provide a smooth, uniform finish. It is done after making prior preparations on the substrate areas that need repair. For best results, the primer should be applied to a clean surface that is free of contaminants or impurities.

Spot priming is done to:

  • Protect repaired spots before applying any coating
  • Provide adhesion to the top coat when painting
  • Provide a sealing effect by preventing moisture or other substances from making contact with the substrate
  • Prevent corrosion on metallic substrates or accessories like nails present on timber substrates

There are various types of primers used in spot priming. Their categories are based on quality and the situations in which they provide the best protection. Some of them include:

  • Bonding primer
  • Acrylic primer
  • Tintable primer
  • Alkyd primer
  • High build primer
  • PVA primer

The right choice of primers is essential because many primers only offer optimal results when used with certain paints.


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