One-Step Conversion Coating for Metal-Polymer Adhesion
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Solution Overview
Problem
Current methods for producing sandwich structures with metallic and organic polymer layers face challenges in achieving high adhesion, particularly with hot-dip galvanized steel sheets, requiring multiple process stages and resulting in insufficient peel tensile strength, and are not adaptable to various metal substrates.
Innovation Solution
A one-step conversion coating process using an aqueous composition containing specific concentrations of zinc, manganese, aluminum, chromium, and polyacrylic acid is applied to metallic surfaces, followed by pressing with organic polymer layers to form a sandwich structure, eliminating the need for activation steps and achieving high adhesion across different metallic substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional wet-chemical conversion compositions are used on hot-dip galvanized steel sheets, then adhesion is improved, but the process complexity increases and peel tensile strength remains insufficient
Solution Approach 1:
The patent combines multiple functions (surface activation, adhesion promotion, and conversion coating) into a single integrated coating composition. This eliminates the need for separate activation steps and multiple treatment stages, reducing process complexity while achieving peel tensile strength of at least 300 N/4cm on hot-dip galvanized steel sheets.
Solution Approach 2:
The coating composition is designed to be universally applicable to various metal substrates (galvanized steel, electrolytically galvanized steel, aluminum, stainless steel) while performing multiple functions simultaneously: surface activation, adhesion promotion, and corrosion protection. This multi-functionality resolves the contradiction by achieving high peel strength without increasing process complexity for different substrates.
2Strength
If multiple process stages are used for surface treatment, then adhesion is improved, but productivity decreases
Solution Approach 1:
The coating composition contains pre-formulated adhesion promoters and surface activators that perform preliminary surface preparation functions during the single coating application. This eliminates the need for separate preliminary treatment stages, maintaining high adhesion while improving productivity by reducing the number of process steps.
Solution Approach 2:
Multiple treatment functions (cleaning, activation, adhesion promotion) are merged into a single coating step. The coating composition is applied once and delivers all necessary surface preparation and bonding functions, significantly improving productivity compared to sequential multi-stage processes.
3Strength
If conventional coating methods are used, then adhesion is achieved on some substrates, but adaptability to various metal substrates is poor
Solution Approach 1:
The coating composition is specifically designed with universal adhesion promoters that effectively bond to various metal substrates including galvanized steel, electrolytically galvanized steel, aluminum, and stainless steel. The composition adapts to different substrate chemistries while maintaining consistent adhesion performance of at least 300 N/4cm across all substrate types.
Solution Approach 2:
The coating composition uses pH-responsive and chemistry-adaptive mechanisms to adjust its binding characteristics based on the substrate type. This allows the same coating formulation to achieve optimal adhesion on diverse metal substrates without requiring substrate-specific formulations, thereby improving adaptability while maintaining high adhesion strength.
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
This method achieves significantly improved peel strength, simplifies the production process, and ensures consistent adhesion across various metallic substrates, meeting the requirement of at least 300 N/4cm peel strength, while reducing the number of process stages and improving bath stability.
Implementation Method 1
a special adhesion-promoting and conversion-protecting coating is applied to at least one surface
Implementation Method 2
contacted with an aqueous conversion composition containing: 0.5 to 20 g/L zinc, 0.01 to 10 g/L manganese, 0.01 to 10 g/L aluminum, 0.01 to 1 g/L chromium(III), 0.01 to 5 g/L iron(II), 0.01 to 5 g/L iron(III) and/or 0.01 to 5 g/L magnesium
Implementation Method 3
the liquid film produced with this is dried
Implementation Method 4
the metallic layer coated in this way is brought into contact with at least one layer based on organic polymer and connected by pressing under pressure and/or temperature to form a sandwich structure
Implementation Method 5
connected by pressing under pressure and/or temperature to form a sandwich structure
Data Source
AI summary
The invention relates to a method for producing a sandwich structure on the basis of at least one layer on the basis of metallic material and on the basis of at least one layer of organic polymer, wherein for coating of at least one metallic surface with at least one metallic layer to be combined with the layer on the basis of organic polymer, an aqueous conversion composition on the basis of zinc, additional cations, poly(acrylic acid), and optionally silane, is brought into contact, wherein the liquid film thereby produced is dried on and wherein the metallic layer coated in such manner is brought into contact with at least one layer on the basis of organic polymer and is combined into a sandwich structure by means of compaction under pressure and/or temperature. The invention also relates to such sandwich structures.