Chromium Electrolyte Self-Replenishing Anode for Gravure Cylinders

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Solution Overview

Problem

The electrolytic deposition of chromium from Cr(III) containing electrolytes results in a decrease in chromium(III) ion concentration over time, requiring frequent dilution and leading to the accumulation of anions and potential formation of toxic Cr(VI) species.

Innovation Solution

Incorporating metallic chromium into the electrolyte, along with chromium(III) salt, formic acid, and specific additives, maintains a stable Cr(III) concentration by facilitating its dissolution and preventing Cr(VI) formation, allowing for prolonged electrolysis without the need for semipermeable membranes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If chromium(III) salt is added to replenish Cr(III) ions during electrolysis, then the Cr(III) concentration is maintained, but anions accumulate in the electrolyte requiring frequent dilution

Engineering Contradiction:

ImproveCr(III) concentrationVSAvoidanion accumulation

Core Design Contradiction:

Quantity of substanceVSLoss of substance

Solution Approach 1:

Metallic chromium serves as a self-dissolving anode that automatically replenishes Cr(III) ions in the electrolyte during electrolysis. The chromium metal oxidizes at the anode to form Cr(III) ions, which then deposit on the cathode, creating a self-sustaining cycle that maintains constant Cr(III) concentration without adding external salts or causing anion accumulation.

Inventive Principle:

Principle #25Self-service

2Productivity

If conventional Cr(III) electrolytes are used, then chromium deposition is achieved, but Cr(VI) formation occurs which is toxic and requires semipermeable membranes

Engineering Contradiction:

Improvechromium depositionVSAvoidCr(VI) formation

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The electrolyte composition is modified by adding specific organic additives (sulfonates, carboxylates, or phosphonates) that form stable complexes with chromium ions. This changes the electrochemical parameters of the system, shifting the deposition potential and preventing the formation of toxic Cr(VI) species while maintaining efficient chromium metal deposition.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Organic complexing agents act as intermediaries between chromium ions and the electrode surface. These additives form stable complexes with Cr(III) that control the deposition process, preventing unwanted side reactions including Cr(VI) formation, and enabling high-quality chromium deposition without toxic byproducts.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If electrolysis continues for extended periods, then production efficiency increases, but Cr(III) concentration decreases requiring electrolyte replacement

Engineering Contradiction:

Improveelectrolysis durationVSAvoidelectrolyte composition stability

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The metallic chromium anode continuously dissolves to replenish Cr(III) ions consumed during cathode deposition. This self-regulating mechanism maintains constant electrolyte composition over extended periods, enabling continuous operation for weeks or months without electrolyte replacement or top-up, thereby dramatically increasing production efficiency.

Inventive Principle:

Principle #25Self-service

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach maintains a constant Cr(III) content for several hours to months, prevents Cr(VI) formation, and enables uniform chromium layer deposition on objects, such as gravure cylinders, with improved quality and reduced maintenance.

Implementation Method 1

when metallic chromium is dissolved during electrolysis, Cr(VI) is not produced

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

the dissolution of the metallic chromium can be observed

Methodology Applied

Scientific EffectDissolution:

Implementation Method 3

electrolytic deposition of chromium from Cr(III) containing electrolytes

Methodology Applied

Scientific EffectElectrolysis: Electrolysis

Implementation Method 4

Cr(III) can be added in the form of chromium(III) salts which, however, will lead to successive accumulation of the anion existent in the salt in the electrolyte

Methodology Applied

Scientific EffectReduction: Reduction

Implementation Method 5

The formic acid that is possibly present in the electrolyte according to the invention serves, for example, to remove the oxygen produced from the chromium(III) salt by transforming it into CO2 and H2O

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Data Source

PatentUS20230160083A1Electrolyte and method for producing chromium layers

Publication Date: 2023.05.25 MASCHFAB KASPAR WALTER GMBH & CO KG

AI summary

Disclosed is an electrolyte for the electrolytic deposition of chromium as a metal, comprising (a) a chromium (III) salt and (b) metallic chromium, the use of the electrolyte for producing chromium layers on rotationally symmetrical components, in particular gravure printing cylinders, and methods, in which this electrolyte is used.