Foam Chemical Conversion Coating for On-Wing Aluminum Repair
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Solution Overview
Problem
Existing Type II chemical conversion coatings for aluminum and aluminum alloy components in aeronautics and aerospace applications require multiple applications due to rapid drying, posing environmental and operator hazards, and are challenging to apply on-wing with complex shapes and orientations.
Innovation Solution
A spray foam chemical conversion coating comprising a non-hexavalent chromium aqueous solution, a foaming agent, and a propellant allows for localized application, minimizing drippage and enabling on-wing repair without special controlled areas, using a foaming agent to stabilize the coating for 1-20 minutes, forming a corrosion-resistant barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid chemical conversion coating is applied to aluminum surfaces, then corrosion protection is achieved, but the coating dries quickly requiring multiple applications and causing operator exposure hazards
Solution Approach 1:
The patent transforms the liquid chemical conversion coating into a foam phase by incorporating foaming agents. This phase transition allows the coating to remain in a stable, non-dripping state on vertical and overhead surfaces, eliminating the need for multiple applications and reducing operator exposure to hazardous liquids while maintaining complete surface coverage for reliable corrosion protection
Solution Approach 2:
The foaming agent acts as an intermediary substance that modifies the physical state of the chemical conversion coating. The foam structure provides a stable matrix that contains the reactive coating solution, allowing it to remain on the surface for the required reaction time (1-20 minutes) without drying or dripping, thereby improving operator safety while ensuring complete corrosion protection
2Ease of repair
If liquid chemical conversion coating is used for on-wing repair, then field maintenance is enabled, but spatial constraints and surface orientation create application challenges
Solution Approach 1:
By converting the liquid coating to a foam phase, the patent enables easy application on complex aircraft surfaces including vertical and overhead areas. The foam's stable structure prevents dripping and allows uniform coverage on spatially constrained surfaces, making on-wing repair practical and straightforward without requiring special positioning or multiple applications
Solution Approach 2:
The foam coating can be applied in localized segments to specific damaged areas on aircraft surfaces. This segmented application approach, combined with the foam's ability to conform to complex geometries, enables precise repair of small areas without affecting surrounding surfaces, simplifying on-wing maintenance operations
3Reliability
If multiple applications of chemical conversion coating are made, then complete coverage is achieved, but application time and material usage increase
Solution Approach 1:
The foam phase provides stable, uniform coverage in a single application. The foam structure maintains the coating solution on the surface for the complete reaction time (1-20 minutes), ensuring thorough coverage and reaction without requiring multiple applications, thereby doubling application efficiency while maintaining reliable corrosion protection
Solution Approach 2:
The foam coating maintains continuous contact with the surface throughout the reaction period, ensuring complete and uniform coverage in one application. This continuous action eliminates the interruptions and potential coverage gaps associated with multiple applications, improving productivity while ensuring reliable corrosion protection
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 spray foam coating provides a single application solution that forms a corrosion-resistant barrier on complex shapes, reducing environmental and operator risks, and ensures complete reaction without multiple applications, maintaining a thin film for electrical conductivity.
Implementation Method 1
a foaming agent and propellant are incorporated into an aqueous CCC to create a spray foam CCC
Implementation Method 2
MIL-DTL-81706 Type II CCCs are used to form a corrosion-resistant protective barrier coating by reaction with the surface of aluminum and aluminum alloy substrates
Implementation Method 3
spraying a foam chemical conversion coating on a surface of a metal substrate
Data Source
AI summary
In one aspect, a spray foam chemical conversion coating includes a non-hexavalent chromium aqueous chemical conversion coating solution, a foaming agent, and a propellant. In another aspect, a method of producing a corrosion-resistant coating includes spraying a foam chemical conversion coating on a surface of a metal substrate, allowing the foam chemical conversion coating to react with the surface, and removing excess foam chemical conversion coating from the surface. The foam chemical conversion coating contains no hexavalent chromium.