The concept explained.
SRI & optimal cleanability of stainless steel
It is important that a surface is smooth, but also not too smooth; when the surface roughness is below Ra = 0,2µm, bacteriological contamination may arise because the adhesion forces between the surface and the bacteria have become larger. In other words, the rule “the smoother the surface, the higher the cleanability ” does not always seem to be true, when it concerns bacteria and micro-organisms (see the images ‘various types of bacteria’, source: Stainless Steel World, article by Ko Buijs). The wetblasting technique improves the reconditioning of stainless steel with the aim of achieving a more hygienic and easy-to-clean surface; indicated by the SRI index (Soil Retention Index). This is a value gives practical information on how many contaminants remain on the surface after a cleaning process.
Independent research concerning the SRI was carried out by TNO. Concluded was that the surface treated with H2Ofinish (with a SRI below 0,010) meets all requirements in terms of hygiene and ability to clean, demanded by the European Hygienic Engineering & Design Group (EHEDG) for the purpose of serving both the food & liquor as the pharmaceutical industry.
The picture above shows an image of how a surface treated with H2Ofinish looks like when looking at it microscopically.
H2Ofinish is an environmental friendly process in which the water with additive forms a suspended medium which is sprayed at pressure onto the surface. This results in an attractive satin gloss finish and also creates a certain pressure build-up on the surface; also known as “peening”. The wetblasting gives a better surface structure and a lower SRI value as bead blasting as with this last process the additive rests will remain at the surface. With wetblasting this is prevented by the waterstream.
We work with the PureFinish process which focusses on the re-using of the water and (environmental friendly) additives after filtering them. The amount and ratio of addivites can be adjusted at any time during the process or can be set when special requirements are needed.