Abrasive treatment (standblast)

Abrasive treatment (standblast)

Abrasive treatment – is cold treatment of metal products surface by damaging it with sand or other abrasive powder sprayed by the air flow. At this type of treatment the sand particles are accelerated out of a sandblaster with the energy of compressed air. Professional skills, high quality equipment and quality control are required to provide effective cleaning by abrasive particles and compressed air. Each element affects the outcome of the whole system. In the process of cleaning the unwanted materials are removed, the material surface is reinforced and becomes ready for coating. With the help of abrasive cleaning the old paint, rust and other contaminants are removed from metal structures. In addition, mill scale forming on the new steel is removed.

Angular abrasive particles add roughness to the surface and create a profile, or hatching.
The quality of metal surfaces preparation for painting and application of metallized coatings shall comply with GOST 9.402-2004 "Paint coatings. Preparation of metal surfaces for painting". The GOST distinguishes four cleaning grade standards for mill scale and corrosion products removal from ferrous metals surface:

  • when viewed with a 6-fold increase, scale and rust are not detected;
  • when viewed with the unaided eye, mill scale, rust, burnt, the remains of molding sand and other non-metallic layers are not detected;
  • no more than 5% of the surface has foundry crust and spots and stripes of closely linked mill scale visible to the naked eye. Slag employs no more than 10% of the 25x25mm plate space on any of the sites of the article surface;
  • rust and flaking scale are removed from the surface.

The following degrees correspond to the mentioned above: Sa 3, Sa 2 1/2, Sa 2, Sa l set by the international standard ISO8501-1: 2007: "Preparation of the steel basis before application of paints and similar coatings. Visual assessment of surface cleanliness. Degrees of corrosion and of bare steel basis preparation after overall removal of previous coatings".

The degrees of preliminary surface preparation. ISO standard defines seven degrees of surface preparation. The specifications often contain the following standards: Preparation of the surface by hand and using power tools: scraping, mechanical wire brushing and grinding – is designated by the letters "St".

ISO-St1. Treatment by hand and using power tools
Before you start cleaning the surface by hand or using power tools, thick layers of rust shall be removed by chipping. Visible stains of oil, grease and dirt must also be removed. After cleaning by hand and using power tools, the surface must be freed of peeling paint and dust.

ISO-St2. Thorough cleaning by hand and using power tools
On looking at the surface with the unaided eye, the substrate should look free of oil, grease, dirt, and from the surrounding scale, rust, paint and foreign substances.

ISO-St3. Fine thorough cleaning by hand and using power tools
The same as for St2, but the substrate must be cleaned much more thoroughly until the metallic luster show up.

ISO-Sa. Abrasive cleaning
Surface preparation by abrasive method is designated by the letters "Sa". Before abrasive cleaning starts, thick layers of rust must be removed by chipping. Visible stains of oil, grease and dirt must also be removed. After abrasive treatment the substrate must be cleaned of dust and debris.

ISO-Sa1. Light abrasive cleaning
When viewed with the naked eye the surface shall be cleaned out from visible oil, grease and dirt stains, and from scale with poor yawn, rust, paint and other foreign substances.

ISO-Sa2. Thorough abrasive cleaning
When viewed with the naked eye the surface shall be cleaned out from visible oil, grease and dirt stains, and from the most part of scale, rust, paint and other foreign substances. Any residual impurity should have firm adherence.

ISO-Sa2.5. Fine thorough abrasive cleaning
When viewed with the naked eye the surface shall be cleaned out from visible oil, grease and dirt stains, and from the most part of scale, rust, paint and other foreign substances. All the remaining traces of contamination should occur only in the form of subtle spots and stripes.

ISO-Sa3. Abrasive cleaning to visually clean steel
When viewed with the naked eye the surface shall be cleaned out from visible oil, grease and dirt stains, and from the most part of scale, rust, paint and other foreign substances. The surface should have a uniform metallic luster.
 
The cost of abrasive treatment starts from 40 UAH per 1m2 depending on the surface type.