Bead Blasting
Introduction
Glass or glass pearl blasting is a common and widely used procedure for giving stainless steel a uniform finish after treatment. Glass blasting of stainless steel has however a number of significant drawbacks. The high breakdown rate of the glass balls means that in practice blasting is with a high percentage of broken balls, resulting in a relatively high surface roughness (2.0-3.0 micron). Glass blasted surfaces have shown in practice to be susceptible to attracting dirt and are difficult to clean. This combination of contamination of surfaceswith high roughness together with difficulty of cleaning allows corrosion to set in even in a relatively mild (ambient) environment.
Advantages of ceramic pearl blasting
Blasting with ceramic pearls is free of the disadvantages described. The breakdown rate for ceramic pearls is a factor of 50 lower. This guarantees that processing will always be conducted with perfectly global pearls (circa 100 micron). This is immediately apparent in the visual result of surfaces that have been blasted with ceramic pearls: a uniform satin finish. Depending on the roughness of the untreated material a roughness less than 1.0 micron can be achieved.Applications
Blasting with ceramic pearls is for this reason suitable for stainless steel products where appearance is important. Examples of this are stainless steel cladding for walls, shop and office fronts, staircases, lifts and road furnishings (cladding of viaducts, traffic signs etc.). Their susceptibility to corrosion under atmospheric conditions is significantly reduced by this treatment.Blasting with ceramic pearls has proved its suitability for the treatment of stainless steel surfaces in for example the food and harmaceutical industries. The lower roughness makes the surfaces much easier to clean. This is certainly true for industries where the contamination consists of microbes. Vecom Metal Treatment B.V. has facilities for ceramic pearl blasting. Using permanent magnets metallic iron is removed continuously. The material can when required be chemically passivated and rinsed with demineralized water after ceramic pearl blasting to remove for 100% residual blasting material. This treatment will also reduce susceptibility to staining (common phenomenon for glass pearl blasting).
The most important reason for pickling stainless steel is in order to remove welding discolouration and alien iron, thus restoring the corrosion resistance of the material completely. By then blasting with ceramic pearls a uniform, satin sheen can be achieved.