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Last updated: February 12, 2019

What Does Surfacer Mean?

Surfacer is an easy sanding paint used to fill surface irregularities. It plays an important role in automotive coating systems. Surfacers offer benefits like flexibility and safeguards to the production process.

Surfacers were originally designated primer surfacers, but their role as a primer diminished with the introduction of anodic electrocoat systems in the 1960s.

There are two types of surfacers: inner and outer. The inner type is very similar to a topcoat. An outer surfacer is of a more conventional nature and topcoat is applied in the normal way.

Surfacers are also known as fillers or middle coats.


Corrosionpedia Explains Surfacer

Surfacers fill surface defects or irregularities. This is necessary to hide any minor imperfections arising from the pressing and assembly process. However, improvements in metal quality have been very significant and this has consequently affected the way surfacers are formulated.

Surfacers possess the following properties:

  • Mechanical properties such as impact and flexibility
  • Stone chip resistance
  • Resistance to water/moisture
  • Good sandability/rectification properties
  • Good even surface
  • Good adhesion

There are three distinct resin systems used in the formulation of surfacers:

  • Alkyds
  • Epoxy esters
  • Synthetic polyesters

Surfacers have traditionally been highly pigmented products, although more recent developments, in line with improved metal quality, have quite low levels of pigment and an appearance which almost lends itself to a topcoat.

In the past surfacers were spray applied in two coats: wet-on-wet over dip primers or phosphated metal (film thicknesses were -45 µm). The first coat was a red (iron) oxide followed by a second, normally gray. The first coat acted as a "guide coat" to control sanding and to provide a measure of corrosion protection.

There is now considerable use of color-keyed surfacers formulated to align to specific-colored topcoats. Although solvent-based surfacers still tend to predominate, water-borne materials, because of their lower pollution and good leveling, are attracting more attention and are widely used in Europe.



Filler, Middle Coat

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