Electrodeposition Coating Composition for Throwing Power and Pinhole Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional electrodeposition coating methods face challenges in achieving excellent throwing power and maintaining a good appearance, particularly when using zirconium chemical conversion treatment agents, which result in thin films and increased gas pinhole generation, while zinc phosphate agents pose environmental and economic concerns due to high metal ion concentrations and sludge production.
Innovation Solution
An electrodeposition coating composition containing a zinc or bismuth compound, an aminated resin, and a curing agent, with specific milligram equivalent and coulombic efficiency values, and a water-dispersed colloid form of the bismuth compound, is used to form a cured film with improved throwing power and reduced gas pinhole generation, compatible with zirconium chemical conversion treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a zinc phosphate chemical conversion treatment agent is used, then corrosion resistance and adhesiveness are improved, but sludge production increases and effluent treatment becomes difficult
Solution Approach 1:
The patent extracts and eliminates the harmful phosphate component from the chemical conversion treatment by using a silane-based treatment instead of zinc phosphate. This substitution removes the source of sludge production while maintaining the protective function through a different chemical mechanism that forms a silane-based conversion layer without generating insoluble phosphate salts.
Solution Approach 2:
The patent changes the chemical parameters of the conversion treatment from zinc phosphate-based to silane-based system. This parameter change fundamentally alters the chemistry from one that produces sludge to one that forms a soluble or non-sludging conversion layer, thereby resolving the contradiction between protection and waste generation.
2Loss of substance
If a zirconium chemical conversion treatment agent is used, then phosphate ion discharge is avoided and sludge production is reduced, but the chemical conversion treatment film thickness becomes very thin
Solution Approach 1:
The patent introduces a silane-based chemical conversion treatment as an intermediary layer between the metal substrate and the electrodeposition coating. This silane layer serves as a mediator that provides both adequate thickness and good adhesion properties, replacing the thin zirconium layer while maintaining environmental benefits by avoiding phosphate discharge.
3Manufacturing precision
If the neutralization percentage of resin emulsion is reduced to improve throwing power, then coating film formation on uncoated parts is improved, but gas pinholes are generated
Solution Approach 1:
The patent changes the chemical composition parameters of the electrodeposition coating, specifically incorporating a carboxylic acid-modified polyester resin that allows for lower neutralization percentages. This parameter change in resin chemistry enables the system to achieve both improved throwing power and reduced gas pinhole formation by altering how the coating responds to electrochemical deposition conditions.
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 composition achieves excellent throwing power and a good appearance for the cured electrodeposition coating film, even with thin zirconium chemical conversion treatment films, while reducing environmental impact and process steps, and suppressing gas pinhole formation.
Implementation Method 1
cationic electrodeposition coating is a coating method performed by dipping an article to be coated as a cathode in a cationic electrodeposition coating composition and applying a voltage across the electrodes
Implementation Method 2
electrodeposition coating composition and an electrodeposition coating method that enable the formation of a cured electrodeposition coating film
Data Source
AI summary
It is an object of the present invention is to provide an electrodeposition coating composition and an electrodeposition coating method that enable the formation of a cured electrodeposition coating film that develops excellent throwing power and exhibits a good appearance. An electrodeposition coating composition of the present invention comprising:at least one compound (A) selected from the group consisting of a zinc compound (A-1) and a bismuth compound (A-2);an aminated resin (B); anda curing agent (C),whereina milligram equivalent (MEQ (A)) of an acid per 100 g of a resin solid content in the composition is 27 or more;a coulombic efficiency of the composition is 30 mg/C or less;a film resistance of a 15-μm-thick uncured electrodeposition coating film formed using the composition is 400 kΩ·cm2 or more; anda coating film viscosity of an electrodeposition coating film obtained from the composition is 3000 Pa·s or less at 50° C.