Rust Grades & Blast-cleaning Grades

How To Evaluate Rust Grades Before Shot Blasting & Blast-cleaning Grades After Shot Blasting ?

Rust Grades

Grade A
Steel surface largely covered with adhering mill scale but little, if any, rust.

Grade B
Steel surface which has begun to rust and from which the mill scale has begun to flake.

Grade C
Steel surface on which the mill scale has rusted away or from which it can be scraped, but with slight pitting visual under normal vision.

Grade D
Steel surface on which the mill scale has rusted away and on which general pitting is visual under normal vision.

Blast-cleaning Grades

Sa1 – Light blast-cleaning
When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from poorly adhering mill scale,rust, paint coatings and foreign matter. See photographs B Sa1, C Sa1 and D Sa1.

Sa2 – Thorough blast-cleaning
When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from poorly adhering mill scale,rust, paint coatings and foreign matter.Any residual contamination shall be firmly adhering. See photographs B Sa2, C Sa2 and D Sa2.

Sa2-1/2 – Very through blast-cleaning
When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from poorly adhering mill scale,rust, paint coatings and foreign matter.Any remaining traces of contamination shall show only as slight stains in the form ofspots or stripes. See photographs A Sa2-1/2, B Sa2-1/2, C Sa2-1/2 and D Sa2-1/2.

Sa3 – Blast-cleaning to visually clean steel
When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from poorly adhering mill scale,rust, paint coatings and foreign matter.It shall have a uniform metallic colour. See photographs A Sa3, B Sa3, C Sa3 and D Sa3.