Imperial Chemical Industries Limited

Brian A Cooke

Michael Brock

Charles W Bromley

Norman A Coombes

A washcoat composition suitable for application to tin-plated mild steel consists of an aqueous carrier medium and a binder comprising specified relative proportions of (A) a thermosetting acrylic polymer in the form of a sterically stabilized dispersion in the aqueous medium and (B) an epoxy resin, the composition additionally containing an acid catalyst, in particular phosphoric acid or chromic acid or an ammonium or amine salt thereof.

Coating compositions

A continuous process for coating ferrous or zinciferous metal substrates using an acidic coating solution of zinc phosphate in the presence of hydrogen peroxide wherein (a) the molar ratio ortho phosphate/zinc in solution is maintained in the range 0.5-3.7, and (b) the coating solution is replenished with hydrogen peroxide, replenishment feed (i) (comprising zinc, ortho phosphate and anion N.sup.n-), and replenishment feed (ii) (comprising alkali), the ratio of the quantities of (i) and (ii) being defined. The acid H.sub.n N has a pK.sub.a value not greater than 3.

Phosphate coating process

The effective concentration of an electroactive ingredient of a coating solution is determined, and may be restored to a desired level, in response to deviations in the voltammetric current sensed at an indicating electrode comprised of a noble metal.

Coating process with voltammetric sensing of the coating solution

Water-soluble lignosulphonate salts when present in an acid metal phosphating solution modify the physical form of sludge produced therein when the solution is used to treat a metal substrate. Process efficiency is improved.

Phosphating process

A method of controlling a continuous process of phosphating metal surfaces in which an acidic zinc phosphate solution is brought to the steady state and there maintained in response to conductivity change, as phosphating proceeds, by addition of replenishments (a) acidic zinc phosphate and (b) alkali metal ion in a definite ratio of addition rates.

Phosphating method with control in response to conductivity change

In a continuous process of phosphating ferrous metal surfaces using an acidic zinc phosphate solution comprising chlorate and optionally nitrate ions, ferrous ion is maintained at low concentration by controlled addition of a rapid acting oxidant, for example nitrite ion.

Phosphating method

Low molecular weight water soluble polymers (molecular weight less than 5 .times. 10.sup.5) which comprise monomer moieties selected from acrylic acid, methacrylic acid, acrylamide and methacrylamide, when present in acid metal phosphating solutions modify the physical form of sludge produced. Process efficiency is improved.

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Knotty Green, United Kingdom

Brian A Cooke