Viscosity-Controlled Conversion Layer Formation

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Solution Overview

Problem

Existing methods for forming chemical conversion layers on metal surfaces, particularly for corrosion protection, face challenges such as limited thickness of the applied electrolyte film, difficulty in dosing the electrolyte, and unsatisfactory anti-corrosion properties due to varying ion concentrations and cracking issues.

Innovation Solution

A method involving an aqueous composition with 1 to 5% by weight of a thickener, adjusted to a viscosity of 50 mPa*s to 2500 mPa*s, containing active components like chromium(III) compounds, vanadium(IV) compounds, phosphomolybdic acid, titanium compounds, or lanthanum compounds, applied in a diffusion-controlled manner to achieve a thicker, crack-free conversion layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a liquid electrolyte solution is used for forming chemical conversion layers, then sufficient mobility of the active component is achieved, but only a very thin electrolyte film can be applied to the surface in local application

Engineering Contradiction:

Improvethickness of electrolyte filmVSAvoiddifficulty in dosing the electrolyte

Core Design Contradiction:

Quantity of substanceVSEase of operation

Solution Approach 1:

The patent changes the physical parameter of viscosity by adding thickeners to the electrolyte solution, transforming it from a free-flowing liquid to a viscous paste. This allows the electrolyte to be applied in thicker films while maintaining controllability during application, directly resolving the contradiction between film thickness and ease of dosing.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a thick electrolyte film is applied to achieve sufficiently thick chemical conversion layer, then better corrosion protection is achieved, but cracking in the conversion layer increases

Engineering Contradiction:

Improvecorrosion protectionVSAvoidcracking in conversion layer

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent modifies the viscosity parameter of the electrolyte by adding thickeners, which controls the rate at which the electrolyte penetrates and reacts with the metal surface. This diffusion-controlled approach allows for the formation of thicker conversion layers without excessive reaction rates that would cause cracking, thus resolving the contradiction between corrosion protection and layer integrity.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If chromium(VI)-containing electrolytes are used for conversion layer formation, then effective corrosion protection is achieved, but significant health risks are posed

Engineering Contradiction:

Improvecorrosion protectionVSAvoidhealth risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the harmful chromium(VI) compounds with chromium(III) compounds, which are less toxic. By combining this substitution with viscosity modification through thickeners, the patent achieves both reduced health risks and maintained or improved corrosion protection performance, effectively converting a harmful process into a safer one.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Ease of operation

If brush or pen application means are used for electrolyte application, then local application is enabled, but difficult dosing control is achieved

Engineering Contradiction:

Improvelocal application capabilityVSAvoiddosing precision

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent changes the viscosity parameter of the electrolyte to create a paste-like consistency that can be easily controlled during manual application with brushes or pens. This viscosity modification enables precise dosing control while maintaining the ability to apply locally, resolving the contradiction between ease of operation and dosing precision.

Inventive Principle:

Principle #35Parameter changes

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 allows for the formation of a thicker, crack-free chemical conversion layer with enhanced corrosion resistance, as demonstrated by a salt spray test showing resistance of over 72 hours, and simplifies the application process by controlling reaction kinetics and ion transport.

Implementation Method 1

diffusion-controlled formation of a chemical conversion layer

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

a viscosity in the range from 50 mPa*s to 2500 mPa*s having; and applying the composition

Methodology Applied

Scientific EffectViscosity modification:

Implementation Method 3

chemical reaction with the metallic substrate, usually by an aqueous treatment solution

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 4

the metal surface is passivated by forming the conversion layer

Methodology Applied

Scientific EffectPassivation:

Data Source

PatentEP2725119B1Method for forming a conversion layer

Publication Date: 2018.12.05 AIRBUS DEFENCE & SPACE GMBH

AI summary

An aqueous composition comprises an active component(s) for the formation of the chemical conversion layer and thickener(s), and has viscosity of 10-10000 mPa.second. Independent claims are included for the following: (1) formation of chemical conversion layer, which involves providing composition and applying the composition on metal surface; and (2) Use of the composition for the formation of a chemical conversion layer on a metal surface.