Sandblasting is a traditional and efficient surface cleaning process for bonding (anchoring) coatings. Improper prior preparation always results in waste of time and materials, burdening maintenance costs and endangering the life of the parts themselves intended to be protected.
Increasing quality control requirements have led to the development of international standards that allow precise specifications of what are called “Degrees of Cleaning” of steel surfaces. The most important is the Swedish standard SIS-05 5900/1967 “Pictorial Surface Preparation Standards for Paiting Stell Surfaces” which sets photographic standards of the Degrees of Oxidation (weathering) to which the part is subjected and the “Degrees of Cleaning” that can be obtained by manual, mechanical and abrasive blasting operations. The need to specify the degree of cleanliness is to establish the minimum acceptable conditions for the perfect anchorage of the coating to be applied, avoiding (or requiring, as the case may be) the surface to be completely clean, without the slightest contamination by scale or oxide, featuring the characteristic light gray color without blemishes, which would require longer operating times, often unnecessarily.
The cited standard establishes four patterns for initial states of surfaces by standardizing the degrees of oxidation they present.

Image description
grade it Grade “A”
is the state of the steel surface immediately after rolling with scale but without oxidation (rust);
grade-b Grade “B”
Surface already with traces of oxidation;
c-grade Grade “C”
Carepa crumbling by oxidation but when it has not yet reached the surface in depth
d-grade Grade “D”
The surface already has cavities in large numbers visible to the naked eye.
It also establishes four “Degrees of Cleaning” for the preparation of abrasive blast steel surfaces for each initial state standard:
b-sa-1 Grade “Sa 1”
Light abrasive blasting (Brush-off) – when the surface was quickly hit by the jet (B Sa 1, C Sa 1 and D Sa 1);
b-sa-2 Grade “Sa 2”
(Commercial) – when blasting was more careful, removing scale, rust and scale, and may have slight visible debris on less than 1/3 of the surface (B Sa 2, C Sa 2 and D Sa 2).
b-sa-3 Grade “Sa 3”
(White Metal) – when the surface is 100% clean (A Sa 3, B Sa 3, C Sa 3 and D Sa 3).
b-sa-2-1-2 Grade “Sa 2 1/2”
(Near-white metal) – when the jet is long enough to remove more than 95% of visible contamination and light gray (A Sa 2 1/2, B Sa 2 1/2, C Sa 2 1/2 and D Sa 2 1/2).

The standard sets only cleanliness standards. To complete the specification of the minimum surface preparation conditions other factors should be considered as absence of oils or greases, contamination that should be avoided (usually citing the recommended abrasive) and the appropriate roughness (usually 20-30% of the coating thickness). , among others.

  • Phone
    +55 (11) 3388-3534

  • Rua Muniz de Souza, 306
    Aclimação, São Paulo - SP

© Copyright 2024 zirtec by getsource