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EPS processed steel has high Ra & low Rz surface for optimum paint performance
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Better Paint Performance With Simpler Pretreatment



  What's Your Paint Pretreatment ?
  • wipedown with solvent-soaked rags prior to a liquid spray?
  • 7-stage phosphate wash/rinse regimen prior to powdercoat?

In either case, EPS steel ordered dry (no oil) can reduce the time and cost of your pretreatment. With no oil to strip off :

  • there's much less wipedown needed for fabricators
  • you can 'lean out' paint pretreatment – eliminate a stage
    or reduce the chemical concentration – with no loss of corrosion protection
  • you can reduce the temperature of the pretreat bath
  • you'll change pretreatment wash solutions less often
  • there'll be no more residual oil to pollute a paint bath

With no oil or trapped chlorides and a surface characterized by a uniform texture of micro 'jagged' peaks and valleys, EPS offers outstanding paint performance – both paint adhesion and corrosion resistance.


Multiple, separate automotive OEM paint tests were conducted on EPS samples prepared and painted in accordance with the standards for vehicle body panels. The tests, performed by accredited testing labs, determined the curing, adhesion, corrosion resistance (salt spray exposure testing) and gasoline/oil resistance of EPS-processed samples. In every test, the EPS samples exceeded industry acceptance criteria.


Additional comparative salt spray and paint adhesion tests performed at other independent testing labs validated this EPS advantage (see all test details).



Paint Performance Explained


The EPS surface is clean – oil and contaminant free – which certainly helps paint performance. But the secret to EPS' superior paint adhesion is its 'engineered' surface texture.


EPS surface is typically 'rougher' than that of acid pickled steel, as measured by its Ra value. The average amplitude of 'peaks and valleys' along the EPS surface tends to be greater, and it also has a more 'jagged' profile of sharper peaks and valleys. This profile holds on to paint better than the lower Ra acid pickled profile.


However, that rougher profile does NOT yield a rougher final painted finish. While the average heights of peaks and valleys are greater, they are also very uniform – heights of peaks don't deviate and depths of valleys don't deviate much from their average. This characteristic, termed low Rz, promotes a smooth, uniform paint appearance.

closeup of EPS pickled steel surface finish
Photo of EPS surface at 200X magnification,
taken with a scanning electron microscope.
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