Brazed Aluminum Coolant Additives for Fluoride Corrosion Control
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Solution Overview
Problem
The widespread use of controlled atmosphere brazing (CAB) in heat exchanger manufacturing leads to localized corrosion of aluminum surfaces due to residual fluoride ions from fluxing agents and increased electrical conductivity in coolants, posing challenges for both traditional and fuel cell-powered vehicles.
Innovation Solution
The development of coolants containing polycarboxylic acid functional compounds as brazed metal corrosion inhibitors, which inhibit the leaching of halogen ions like fluoride, thereby reducing corrosion and maintaining low electrical conductivity, is proposed. These compounds include maleated tall oil fatty acids and their derivatives, which are added to the coolant in specific concentrations to provide effective corrosion protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If brazing fluxes are used to join aluminum heat exchanger components, then the components are permanently joined together, but residual fluoride ions remain on the brazed surfaces causing localized corrosion
Solution Approach 1:
The patent converts the harmful fluoride ions left by brazing fluxes into beneficial complexes by adding fluoride-sequestering compounds (such as lanthanum, cerium, or other rare earth metals) to the coolant. These compounds bind the fluoride ions to form stable, non-corrosive complexes, thereby eliminating the corrosion problem while maintaining the benefits of brazed joints.
Solution Approach 2:
The patent introduces an intermediary substance (fluoride-sequestering compound) that mediates between the harmful fluoride ions and the aluminum brazed surfaces. This intermediary binds the fluoride ions in solution, preventing them from attacking the metal surfaces, thus protecting the system without requiring changes to the brazing process itself.
2Temperature
If conventional coolants are used in fuel cell systems, then heat removal is achieved, but electrical conductivity increases leading to efficiency problems
Solution Approach 1:
The patent changes the chemical composition parameters of the coolant by selecting organic acid-based coolants (such as HOAT or OAT formulations) with specific corrosion inhibitor packages that maintain low electrical conductivity. The coolant formulation is optimized to achieve the required heat transfer properties while keeping ionic content low to minimize electrical conductivity and associated energy losses in fuel cell systems.
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 use of these corrosion inhibitors significantly reduces corrosion on brazed aluminum surfaces and maintains low electrical conductivity in fuel cell coolants, enhancing the durability and safety of cooling systems in vehicles.
Implementation Method 1
The use of polycarboxylic acid functional compounds as brazed metal corrosion inhibitors, which are added to coolants to prevent leaching of halogen ions like fluoride, thereby reducing corrosion
Implementation Method 2
The coolant is then forced to flow through a heat exchanger (e.g., a radiator) to be cooled down by air
Implementation Method 3
The coolant flows back to the coolant tank where it can be pumped back to the heat sources of the vehicle to again remove excess or undesirable heat
Implementation Method 4
heat exchangers have been increasingly formed by a brazing operation, wherein the individual components are permanently joined together with a brazing alloy
Data Source
AI summary
Disclosed are coolants comprising brazed metal corrosion inhibitors. In one embodiment, the disclosed brazed metal corrosion inhibitor will comprise a polycarboxylic acid functional compound having the structure: wherein R1, R2, R3, and R4 are each independently selected from the group consisting of H, OH, COOH, C1-C10alkyl groups, glycol esters, anhydride groups, —COOM, and combinations thereof, wherein M is at least one of H, alkali metal ions, alkali earth metal ions, NH4+, amines, imidazoline, polyalcohol esters, C1 to C12 alkyl groups, and combinations thereof; wherein (1) at least three of R1, R2, R3, and R4 contain the group —COOM, wherein M is defined above; or (2) at least two of R1, R2, R3, and R4 contain an anhydride group, and at least one of R1, R2, R3, and R4 contain the group —COOM, wherein M is defined above.