Preliminary treatment standards
7.1 Scraping and wire -brushing
It is assumed that, before
this treatment takes place, the steel surface has been cleaned of dirt, oil and
grease and that the worst instances of rust have been removed by chipping.
St 2 Thorough hand scraping, hand
wire brushing, hand sanding, etc.: This treatment should remove all loose mill
scale, rust, paint and contaminants. Finally, the surface must be cleaned with
a vacuum cleaner, clean and dry compressed air, or a clean brush. The substrate
should then have a faint metallic sheen. The surface should have the same
appearance as illustrated in the St 2
series of pictures.
St 3 Very thorough hand scraping, hand wire brushing, hand sanding etc.: surface pre-treatment as in St 2 but much more thorough. After the fine particles have been removed, the surface should have a pronounced metallic sheen. The surface should have the same appearance as illustrated in the St 3 series of pictures.
7.2 Blast cleaning
It is assumed that, before this treatment takes place, the surface has
been cleaned of dirt, oil and grease, and that the worst instances of rust have
been removed by chipping.
Sa 1 Brush-off blast cleaning: leading to removal of loose mill scale, rust, paint and contaminants.
Sa 2 Thorough (Commercial) blast cleaning: leading to removal of nearly all
mill scale, rust, paint and contaminants.
Sa 2½ Very thorough (Near-White) blast cleaning: leading to removal of
practically all mill scale, rust, paint and contaminants to such an extent that
only slight traces in the form of very light shadows or streaks remain behind.
Sa 3 White metal blast cleaning: leading to complete removal of all mill
scale, rust, paint and contaminants.
The following applies in general to Sa 1, Sa 2, Sa 2½ and
Sa 3: finally, the surface must be cleaned with the help of a vacuum
cleaner, clean and dry compressed air, or a clean brush. The surface appearance
must be the same as the picture illustrating the standard.
