Wet blasting is a new surface treatment that improves the hygiene of stainless steel surfaces when working with powders. The process is very suitable for equipment used in the food industry, where the finish requirements are becoming increasingly stringent.
Wet blasting involves treating a surface with a pressurized mix of water and blasting agent. This enormously improves the adhesion properties, which results in:
- a strong reduction of bacterial growth and microbial contamination in your production process;
- optimum corrosion-resistance;
- significant improvement of the cleanability.
Wet blasting makes the magnetic separator superbly suited for the food industry, and the separator therefore meets all the standards applicable to this industry, such as EN1672-2, EN ISO14159, 2006/42/EC, (EC)1935/2004 and EHEDG.
Recent research by TNO (Netherlands Organisation for Applied Scientific Research) shows that it is not the surface roughness value (Ra) but rather the soil retention index (SRI) that is the determining factor for how much protein is left behind. The SRI indicates the overall surface characteristics. The lower this value, the less adhesion, and thus the less product that remains behind.
In fact, according to TNO, certain bacteria actually adhere better to extremely smooth surfaces (Ra value ≤ 0,2 µm)! Therefore, with the hygienic wet blasting process, surfaces that are ‘too smooth’ are slightly roughened to give them the ideal characteristics. The final Ra value is approximately 0.3 to 0.6 µm. Moreover, this ‘green’ treatment does not involve the use of any environmentally harmful chemical products.
Wet blasting is a much milder process than dry blasting, yet it is just as effective.
During dry blasting, with glass beads for example, the impact of the blasting agent actually breaks open the surface. The surface is then clean, but because the resulting surface has an open structure, it is susceptible to scratching, corrosion and adhesion of contaminants. This is the big difference with wet blasting: a finer blasting agent is used, and the impact is evenly distributed by the damping effect of the water, resulting in a much more even finish.
Comparable processes are Purefinish (developed by Rössler), hygienic surface treatment (developed by The Stainless Solutions Group) and Viwateq.
The hygienic wet blasting cabinet purchased by Goudsmit was built by Rössler and developed in collaboration with TNO.