Post-Anodization Sealing of Aluminum Alloys
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Solution Overview
Problem
Current anodizing processes for aluminum alloys, particularly 'difficult' alloys like 2214 and 2618A, face challenges in providing adequate corrosion resistance due to defects in the anodic layer, and are impacted by European REACH regulations prohibiting hexavalent chromium use.
Innovation Solution
A post-anodization sealing process involving impregnation in a hexafluorozirconate salt and trivalent chromium salt aqueous bath, followed by sealing in a silicate solution and a post-clogging rinse, to enhance the corrosion resistance of aluminum alloys while being compliant with REACH regulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional anodizing processes are used on difficult aluminum alloys, then the anodic layer can be formed, but the layer contains defects leading to insufficient corrosion resistance
Solution Approach 1:
The patent applies preliminary action by performing an impregnation treatment before the final sealing step. The anodic layer is first impregnated with a solution containing zirconium compounds and other metals, which prepares the layer structure to better resist corrosion. This preliminary impregnation modifies the porous structure to prevent defect propagation and improve overall layer quality before sealing completes the protection.
2Reliability
If hexavalent chromium is used in anodizing and sealing processes, then corrosion resistance is improved, but the process violates European REACH regulations
Solution Approach 1:
The patent extracts and removes hexavalent chromium from the anodizing and sealing processes while maintaining corrosion protection. The method uses alternative compositions including zirconium compounds, titanium compounds, and other non-hexavalent chromium metals to achieve the same protective function without the harmful toxic effects, thereby complying with REACH regulations.
Solution Approach 2:
The patent employs disposable or replaceable sealing compositions that do not rely on persistent hexavalent chromium. The sealing layer is formed using soluble salts and compounds that can be applied and rinsed off, providing protection without introducing long-term environmental contaminants. This approach allows compliance with regulations while maintaining effective corrosion resistance.
3Reliability
If the anodic layer is sealed using conventional methods, then the pores are closed, but the anti-corrosion performance is insufficient for difficult aluminum alloys
Solution Approach 1:
The patent uses composite materials in the sealing process by combining multiple metal compounds including zirconium compounds, titanium compounds, and other metals in the impregnation solution. This composite approach creates a multi-component protective layer that leverages the synergistic effects of different metals to achieve superior corrosion resistance that cannot be obtained with single-material sealing methods.
Solution Approach 2:
The patent segments the sealing process into distinct steps: first an impregnation step with a multi-component solution containing various metal compounds, followed by a separate sealing step. This segmentation allows each step to be optimized independently - the impregnation step introduces protective compounds into the porous structure, while the sealing step closes the pores, resulting in enhanced overall performance.
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
The process significantly improves the anti-corrosion properties of 'difficult' aluminum alloys, maintaining corrosion resistance even after Hard Anodic Oxidation treatment, and is applicable to various anodization methods, ensuring compliance with European REACH regulations.
Implementation Method 1
a step of impregnating the anodized aluminum or aluminum alloy, in an aqueous bath of demineralized water containing a hexafluorozirconate salt and a trivalent chromium salt
Implementation Method 2
a sealing step carried out in an aqueous solution of deionized water having a conductivity less than or equal to 100 μS/cm containing between 1 and 500 g/L of an alkali metal or alkaline earth metal silicate
Data Source
Figure 1
AI summary
The invention relates to a method for post-anodisation sealing of aluminium or aluminium alloy. The invention also relates to a method for the surface treatment of an aluminium or aluminium alloy part intended for use in the aviation sector, comprising at least the following steps: i) subjecting said part to an anodisation step; ii) treating the anodised part with a post-anodisation sealing method according to the invention; and optionally iii) applying one or more layer(s) of paint; or optionally iv) applying a hard anodic oxidation treatment to at least some of the functional areas of the part. The invention also relates to a part made of aluminum or an aluminum alloy treated with a post-anodisation sealing method according to the invention, optionally comprising one or more layer(s) of paints or optionally having, on certain functional areas, a hard anodic oxidation treatment, said part being intended for use in the aviation sector.