Brazed Surface Flux Removal for Coating Adhesion
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Solution Overview
Problem
The existing methods for preparing aluminum heat exchangers for coating are hindered by the presence of a flux layer, which includes a powder component that inhibits effective wetting and adhesion of subsequent coating layers, leading to delamination issues due to the inability to effectively remove the flux layer using acid or base etching techniques.
Innovation Solution
A method involving an aqueous solution of potassium fluoride (KF) is applied to the brazed surface to partially or completely remove the powder component of the flux layer, allowing for subsequent coating adherence without delamination, with concentrations ranging from 2.5% to 3.5% by weight and immersion times of 30 to 180 seconds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If acid or base etching techniques are used to remove the flux layer, then the powder component should be removed, but these methods fail to effectively remove the flux layer for suitable coating application
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by using specific concentrations of hydrofluoric acid (5-15%), nitric acid (5-15%), or phosphoric acid (5-15%) either individually or in combination. These optimized parameter ranges enable effective flux layer removal that was not achieved by conventional etching methods, allowing subsequent coating layers to adhere properly to the brazed surface
2Ease of manufacture
If the flux layer is left on the surface after brazing, then the brazing process is simplified, but the powder component inhibits effective wetting and coating adhesion
Solution Approach 1:
The patent extracts and removes the harmful powder component of the flux layer through controlled chemical etching using acid solutions. This selective removal process eliminates the substance that prevents coating adhesion while preserving the underlying conversion coating and brazed surface, thereby enabling effective coating application without complicating the brazing process itself
3Reliability
If a coating is applied over the powder layer, then odor prevention and anti-corrosion features are provided, but the coating delaminates over time
Solution Approach 1:
The patent performs preliminary removal of the powder component through acid etching before coating application. By eliminating the contaminating powder layer in advance, the subsequent coating can directly bond to the conversion coating and metal substrate, ensuring long-term stability and preventing delamination while maintaining the protective and odor-prevention functions
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 KF treatment effectively removes the flux layer, enabling better adhesion and application of subsequent coating layers, such as odor prevention or anti-corrosion coatings, by creating a suitable surface for coating without delamination.
Implementation Method 1
applying an aqueous solution containing a flux-removing agent to the surface to at least partially remove the powder component of the flux layer
Data Source
AI summary
According to one embodiment of the present invention, a method for preparing a brazed surface to receive a coating is disclosed. The method includes providing a brazed surface having a flux layer including a conversion coating and a powder component; and applying an aqueous solution containing a flux-removing agent to the surface to at least partially remove the powder component of the flux layer to obtain a treated brazed surface that is suitable for receiving a subsequent coating layer.