Alterenative Process for Pickling and Passivation of Stainless Steel

British surface engineering specialist Poligrat (UK) Ltd. has developed a new environmentally friendly alternative to the traditional acid pickling and passivation treatment for austenitic stainless steels. With traditional acid pickling processes, the acid removes the upper surface of the material – including the existing passive layer, impurities and any residual extraneous material from manufacturing processes – so as to produce a metallic clean surface on which a new and homogeneous passive layer can be formed. This means that the external dimensions of the component will be changed slightly due to the small amount of surface removal.

The new POLINOX Protect system works in a different manner as it changes the structure and composition of the existing passive layer, so the dimensions of the component are not changed. POLINOX Protect is a water based solution of a special blend of proprietary chemicals which are bio-degradable and not poisonous, and the process does not produce any noxious or dangerous fumes. The new process works by breaking down the iron oxides – which reduce the corrosion resistance of the stainless – within the existing passive layer and heat treatment products. This breakdown produces free iron which is removed along with any iron contamination of the surface. The chromium and nickel oxides already existing on the surface remain untouched, so forming the passive layer.

For more information contact: Poligrat (UK) Ltd., Aldershot, UK. Tel: 44 1252 336337, Fax: 44 1252 322791, Web: www.poligratuk.co.uk.


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