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Macdermid Acumen, Inc.

Richard Tooth

Roderick Dennis Herdman

Roshan V Chapaneri

Terence Clarke

Stacey Handy

Trevor Pearson

Marc Mertens

Stacey Hingley

Roderick D Herdman

Stacey L Handy

A method of treating a substrate, wherein the substrate comprises a layer deposited from a trivalent chromium electrolyte, is described. The method includes the steps of providing an anode and the chromium(III) plated substrate as a cathode in an electrolyte comprising (i) a trivalent chromium salt; and (ii) a complexant; and passing an electrical current between the anode and the cathode to passivate the chromium(III) plated substrate. The substrate may be first plated with a plated nickel layer so that the chromium(III) plated layer is deposited over the nickel plated layer.

Passivation of micro-discontinuous chromium deposited from a trivalent electrolyte

A method of adjusting and controlling the color of trivalent chromium deposits is provided. The method includes the steps of: (a) measuring the color of a trivalent chromium deposit standard; (b) adding one or more color enhancing additives to a trivalent chromium electrolyte; (c) contacting the substrate with the trivalent chromium electrolyte containing the one or more color enhancing additives to deposit trivalent chromium on the substrate; (d) measuring the color of the color-enhanced trivalent chromium deposit; (e) comparing the color of the color-enhanced chromium deposit to that of the standard; and (f) if necessary, adjusting the amount of the one or more color enhancing additives added to the trivalent chromium electrolyte if the color of the color-enhanced chromium deposit is outside of a desired optical variation from that of the standard color-enhanced chromium deposit. The color of the trivalent chromium deposit may be measured using a spectrophotometer.

Color control of trivalent chromium deposits

An aqueous acidic trivalent chromium electrolyte comprising trivalent chromium ions and a complexing agent for maintaining the trivalent chromium ions in solution is provided in which the aqueous electrolyte comprises additives capable of producing a coating on a substrate having a desired dark hue. The additives typically comprise a dispersion of colloidal silica and an additional additive selected from thiocyanate ions and/or iron ions. The electrolyte is used in a method of producing the desired dark-hued decorative chromium coating on a substrate by electrodeposition.

Dark colored chromium based electrodeposits

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West Midlands, United Kingdom

Richard Tooth