Alkaline Etching for Aircraft Metal Substrate Corrosion Protection
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Solution Overview
Problem
Large scale metal items and structural components used in aircraft production are susceptible to corrosion and environmental degradation, and existing surface treatment methods for inorganic finishes can have undesirable effects on the substrate surface.
Innovation Solution
A method involving degreasing, first and second alkaline cleanings, etching with an alkaline etchant solution, deoxidizing, and optionally additional etch cleaning and deoxidizing, followed by electrolytic deposition of an inorganic finish onto the processed metal substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional acid pickle surface treatment is used to apply inorganic finishes, then corrosion protection is achieved, but undesirable effects on the substrate surface occur
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by using alkaline etchants instead of conventional acid pickles. This fundamental parameter change allows achieving corrosion protection while avoiding the harmful effects associated with acid-based treatments on the substrate surface.
Solution Approach 2:
The patent converts the typically harmful alkaline environment into a beneficial process by using controlled alkaline etching to create the desired surface morphology for inorganic finish application, thereby achieving corrosion protection without the detrimental effects of conventional acid treatments.
2Manufacturing precision
If multiple cleaning and etching steps are performed to achieve smooth surface, then surface roughness is reduced, but process complexity increases
Solution Approach 1:
The patent segments the surface treatment process into distinct sequential steps: degreasing, first alkaline cleaning, alkaline etching, deoxidizing, second alkaline cleaning, and inorganic finish application. This segmentation allows each step to be optimized independently to achieve the target surface roughness of 250 μin or less.
Solution Approach 2:
The patent performs preliminary alkaline cleaning and etching steps before the final inorganic finish application to pre-condition the substrate surface. This preliminary action ensures the surface is properly prepared with the desired roughness characteristics before coating, reducing the need for additional post-processing steps.
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 method achieves a surface roughness of 250 μin (6.4 μm) or less, providing effective corrosion protection in a salt fog environment for at least 336 hours without significant pitting.
Implementation Method 1
etching the metal substrate with an alkaline etchant solution to form an etched metal substrate
Implementation Method 2
deoxidizing the etched metal substrate to form a processed metal substrate
Implementation Method 3
depositing a coating onto the processed metal substrate... comprising electrolytically depositing an inorganic finish
Implementation Method 4
performing a first alkaline cleaning on the metal substrate; performing a second alkaline cleaning on the processed metal substrate
Data Source
AI summary
The present disclosure relates to substrate surface treatment methods and compositions. In at least one aspect, a method includes degreasing a metal substrate; performing a first alkaline cleaning on the metal substrate; etching the metal substrate by electropolishing techniques or with an alkaline etchant solution to form an etched metal substrate, wherein the etched metal substrate comprises an average surface roughness (Ra) of about 8 μin (0.2 μm) to about 16 μin (0.4 μm); deoxidizing the etched metal substrate to form a processed metal substrate; performing alkaline cleaning on the processed metal substrate; optionally performing etch-cleaning and deoxidizing if needed to remove oxides and depositing a coating onto the processed metal substrate to form a coated metal substrate.