#From dust free iso#
#From dust free free#

The standard to assess dust on cleaned steel surfaces is ISO 8502, Preparation of Steel Substrates Before Application of Paints and Related ProductsвЂ“Tests for the Assessment of Surface CleanlinessвЂ“Part 3: Assessment of Dust on Steel Surfaces Prepared for Painting (Pressure-Sensitive Tape Method).

#From dust free free#

So how is вЂњvisually free of dust determined?вЂќ?ДЇor any test to be meaningful, it must be performed in a consistent manner, which is why there are consensus-based standards in the coatings industry that may be invoked in contract documents. Even wiping with a gloved hand or white cotton cloth is not recommended as fibers from the cloth can catch on the roughened (blast cleaned) steel, gloves may be contaminated with dirt or oils and the pressure used, and distance wiped, is inconsistent and therefore not meaningful.

Wiping the surface with a bare hand will contaminate the prepared surface with moisture, oils, and salts from perspiration. The lack of contrast of dust on steel can further complicate the assessment.

Visually assessing the substrate for dust can be difficult since there is no gage that quantifies surface dust concentrations. But just how вЂњcleanвЂќ does the surface need to be? A common statement in painting specifications or product data sheets (PDS) will include some variation of вЂњa blast cleaned surface, when viewed without magnification, shall be free of all visible oil, grease, dust, dirt, mill scale, rust, coating, oxides, corrosion products, and other foreign matter.вЂќ For this article, we will focus on visible dust. To prevent the coating from peeling, flaking, or other types of adhesion loss, the surface must remain clean. When it comes to coatings, surface preparation and surface cleanliness are the foundation, and both can significantly impact the performance of the coating system.ДЄpplication of a coating over dust will prevent it from adhering to either the substrate or the previous coat. As the old adage goes, a house is only as strong as the foundation it is built on. Either the surface preparation was inadequate, the surface was contaminated, or the coating was mixed or applied incorrectly. When a coating system fails prematurely, it is rarely because of the coating itself.