Ciba-geigy Corporation

James Roger Hargreaves

John Burrows

Peter Miles

Arthur Harris

Addition compounds of sulfur dioxide and Schiff bases from primary aliphatic or araliphatic amines and aromatic aldehydes can be used for the sealing of the surface of phosphated mild steel. As a result of this the corrosion resistance of the steel and the adhesion of paint coatings on the treated steel are increased substantially. The addition compounds may have three different structures depending on the components used. They can be prepared easily by passing a stream of SO.sub.2 through the solution of the Schiff base.

Corrosion inhibitors

Process for inhibiting corrosion by corrosive water systems on metals which comprises adding to the water systems a phosphonic acid having the general formula: ##STR1## wherein R.sup.1 is a straight chain alkyl group having 1-5 carbon atoms, an alkenyl group having 3-5 carbon atoms in which the double bond is not adjacent to the nitrogen atom, a tolyl group, a benzyl group or a cyclohexyl group.

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Sale, United Kingdom

James Roger Hargreaves