Air Data Probe Corrosion Protection via ALD
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Solution Overview
Problem
Air data probes face issues with external and internal corrosion, particularly due to sulfur exposure, which affects their heater function and requires improved corrosion protection that is also resistant to erosive conditions like rain and sand.
Innovation Solution
A method involving vapor deposition of a corrosion-resistant ceramic coating on both internal and external surfaces of metallic air data probes using chemical vapor deposition (CVD) or atomic layer deposition (ALD), employing precursors like Al, Si, Ti, and Zr to form oxide or nitride coatings, potentially combined with a noble metallic layer for enhanced protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bulk deposition coating is applied to the air data probe, then corrosion resistance is improved, but the coating porosity increases and internal corrosion protection is insufficient
Solution Approach 1:
The patent changes the deposition parameters by using atomic layer deposition (ALD) instead of conventional bulk deposition methods. This results in a thin, dense, and pinhole-free coating that provides superior corrosion protection while maintaining low porosity, directly resolving the contradiction between corrosion resistance and coating quality
Solution Approach 2:
The patent applies a localized thin film coating specifically to the air data probe surfaces requiring protection. The coating is deposited only where needed (internal and external surfaces) with precise thickness control, providing targeted corrosion protection without the compromises of bulk deposition methods
2Reliability
If a thick corrosion resistant coating is applied to protect against sulfidation, then heater function protection is improved, but the coating becomes more susceptible to erosion from rain, wind, and sand
Solution Approach 1:
The patent changes the coating thickness parameter from thick to thin, and changes the deposition method to ALD which creates a dense, pinhole-free structure. This thin but dense coating provides sulfidation resistance while presenting a smooth, compact surface that is more erosion-resistant than thick, porous coatings
Solution Approach 2:
The patent uses a composite approach by depositing the ceramic coating (such as alumina, silica, or zirconia) in a controlled ALD process that creates a multi-layered or gradient structure at the micro-scale, providing both chemical resistance to sulfidation and physical resistance to erosion
3Duration of action of stationary object
If internal corrosion protection is enhanced to prevent sulfur penetration, then heater lifetime is improved, but the coating complexity and deposition process difficulty increase
Solution Approach 1:
The patent replaces complex mechanical or manual coating application methods with atomic layer deposition (ALD), a vapor-phase deposition technique. This substitution provides automatic, uniform, and precise coating application that enhances heater lifetime through superior corrosion protection while actually simplifying the overall process control and quality consistency
Solution Approach 2:
The ALD process is self-limiting and self-regulating, where each deposition cycle automatically forms a uniform monolayer thickness. This self-service characteristic ensures consistent internal corrosion protection and heater lifetime extension without requiring complex process intervention or monitoring
4Reliability
If a uniform coating is deposited on complex probe geometries to ensure complete coverage, then corrosion protection is improved, but the deposition process time and resource requirements increase
Solution Approach 1:
The patent replaces line-of-sight mechanical coating methods with vapor-phase atomic layer deposition. The vapor precursor can penetrate and deposit uniformly on complex internal geometries, ports, and surfaces that are inaccessible to brush or spray methods, ensuring complete coverage while maintaining efficient batch processing
Solution Approach 2:
The ALD deposition process has universal applicability to all internal and external surfaces of the air data probe regardless of geometry complexity. A single deposition process can coat probes with varying geometries, internal ports, and heating elements uniformly, providing multi-functional coverage without requiring multiple specialized coating 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 solution provides a pin-hole free, uniform, and thin ceramic coating that enhances corrosion resistance, maintains aerodynamics, and extends heater lifetime by reducing sulfidation and erosion, while being cost-effective and applicable to complex geometries.
Implementation Method 1
vapor depositing can include using chemical vapor deposition (CVD)
Implementation Method 2
vapor depositing can include using chemical vapor deposition (CVD) or atomic layer deposition (ALD)
Implementation Method 3
placing the metallic air data probe in a vacuum chamber and evacuating the vacuum chamber before using vapor deposition
Implementation Method 4
The second precursor can be an oxide former including water, ozone, or O2 plasma
Implementation Method 5
Certain embodiments can utilize a cationic species (Ti, TiAl, Ta, Zr) with nitride formers of ammonia, plasma assisted ammonia, plasma assisted nitrogen (N2), or hydrazine
Implementation Method 6
Applying the first precursor can include applying heat simultaneously (e.g., about 500 degrees C.)
Data Source
AI summary
A method can include vapor depositing a corrosion resistant coating to internal and external surfaces of a metallic air data probe. For example, vapor depositing can include using atomic layer deposition (ALD). The method can include placing the metallic air data probe in a vacuum chamber and evacuating the vacuum chamber before using vapor deposition. The corrosion resistant coating can be or include a ceramic coating. In certain embodiments, vapor depositing can include applying a first precursor, then applying a second precursor to the first precursor to form the ceramic coating.