Aqueous electroplating bath
AssigneeSavroc Ltd
InventorsJussi Räisä, Arto Yli-Pentti
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Abstract
An object comprising a chromium-based coating on a substrate is disclosed, wherein the chromium is electroplated from an aqueous electroplating bath comprising trivalent chromium cations, wherein the chromium-based coating comprises 87-98 weight-% of chromium, 0.3-5 weight-% of carbon, and 0.1-11 weight-% of nickel and/or iron, and wherein the chromium-based coating has a Vickers microhardness value of 1000-2000 HV, and wherein the chromium-based coating does not contain chromium carbide. Further is disclosed a method for its production, and an aqueous electroplating bath.
Claims11
A method for producing an object comprising a chromium-based coating on a substrate, wherein the method comprises:
- depositing a chromium-containing layer on the substrate by subjecting the substrate to at least one electroplating cycle from an aqueous electroplating bath,
- wherein each of the at least one electroplating cycle is carried out at a current density of 50-300 Amperes per 1 square decimeter (A/dm2) and at a deposition rate of 1.5-10 micrometers (μm)/minute, and wherein the aqueous electroplating bath comprises:
- trivalent chromium cations in an amount of 0.12-0.3 mole per liter (mol/l),
- iron cations and/or nickel cations in an amount of 0.18-6.16 millimoles per liter (mmol/l), and
- carboxylate ions in an amount of 1.22-7.4 mol/l, and
- wherein the molar ratio of trivalent chromium cations to the carboxylate ions is 0.015-0.099, and wherein the pH of the aqueous electroplating bath is 2-6,
- to produce a hard chromium-based coating having a Vickers microhardness value of 900-2000 HV without subjecting the deposited chromium-containing layer to a heat treatment, and
- wherein the chromium-based coating does not contain chromium carbide.
An aqueous electroplating bath:
- trivalent chromium cations in an amount of 0.12-0.3 moles per liter (mol/l),
- iron cations and/or nickel cations in an amount of 0.18-6.16 millimoles per liter (mmol/l), and
- carboxylate ions in an amount of 1.2-7.4 mol/l, and
- wherein the molar ratio of trivalent chromium cations to the carboxylate ions is 0.015-0.099, wherein the pH of the aqueous electroplating bath is 2-6;
- and
- wherein the conductivity of the aqueous electroplating bath is 160-400 milli-siemens per centimeter (mS/cm).
Dependencies are inferred from the claim text.