Zirconium Passivation Coating Without Fluoride Post-Treatment
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Solution Overview
Problem
Existing anti-corrosion methods for metal substrates often result in coatings with poor corrosion properties due to residual fluoride content and require multiple steps, including post-treatments, and are not environmentally friendly, especially when applied to aluminum substrates.
Innovation Solution
A method using an aqueous zirconium-based anti-corrosion agent with polycyclic hydrocarbons having anellated benzene rings with ortho-substituted hydroxyl groups, applied via a dry-in-place method, which is free of fluoride-releasing compounds and passivating chromium-containing compounds, ensuring effective passivation and paint adhesion without the need for additional post-treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional aqueous anti-corrosion agents based on fluoro complexes of zirconium are applied by drying a wet film, then a coating is formed on the metal substrate, but the coating contains considerable fluoride which results in poor anti-corrosion properties or requires post-treatment
Solution Approach 1:
The invention extracts and removes fluoride from the anti-corrosion agent formulation. The aqueous anti-corrosion agent is specifically designed to be free of fluoride-releasing compounds, thereby eliminating the source of harmful fluoride in the dried coating while maintaining effective anti-corrosion performance through alternative chemistry.
Solution Approach 2:
The invention changes the chemical composition parameters of the anti-corrosion agent by replacing fluoro complexes with non-fluoride-based zirconium compounds. This parameter change eliminates fluoride release while maintaining the passivation capability on aluminum substrates, resolving the contradiction between coating effectiveness and harmful fluoride content.
2Reliability
If conventional anti-corrosion methods are used to achieve adequate passivation, then corrosion protection is provided, but multiple treatment steps including post-treatments are required
Solution Approach 1:
The invention merges the pickling and passivation functions into a single integrated treatment step. The aqueous anti-corrosion agent simultaneously performs both functions without requiring separate post-treatment steps, thereby simplifying the overall process while maintaining effective passivation on aluminum substrates.
Solution Approach 2:
The aqueous anti-corrosion agent is designed with multi-functionality, serving both as a pickling agent and a passivation agent in one application. This universal formulation eliminates the need for multiple specialized treatment steps, reducing process complexity while achieving adequate corrosion protection.
3Ease of manufacture
If conventional anti-corrosion agents containing fluoride-releasing compounds are used, then pickling effect on metal substrate is achieved, but environmental concerns arise
Solution Approach 1:
The invention converts the harmful fluoride-releasing chemistry into beneficial non-fluoride-based chemistry. By replacing fluoro complexes with alternative zirconium compounds, the formulation maintains effective pickling capability on aluminum substrates while eliminating environmental harm from fluoride release, thus converting a harmful approach into a beneficial one.
Solution Approach 2:
The invention changes the chemical parameters of the anti-corrosion agent by eliminating fluoride-releasing compounds from the formulation. This parameter change maintains the necessary pickling effectiveness for aluminum substrate treatment while removing the environmental harm associated with fluoride release, resolving the contradiction between manufacturing effectiveness and environmental protection.
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 method provides excellent anti-corrosion results with a homogenous surface coating on metal substrates, particularly aluminum, achieving effective paint adhesion and reducing environmental concerns by minimizing fluoride content and simplifying the process to a single-step dry-in-place application.
Implementation Method 1
the surface of the metal substrate is brought into contact with an aqueous anti-corrosion agent which contains at least one water-soluble compound (A) of the element zirconium... in which method the surface of the metal substrate is brought into contact with an aqueous anti-corrosion agent which contains at least one water-soluble compound (A) of the element zirconium
Implementation Method 2
During the drying process, all of the active components of the anti-corrosion agent that do not transition into the gaseous state during drying are usually deposited on the metal substrate
Data Source
AI summary
A method for anti-corrosion pre-treatment of metal substrates using zirconium-based aqueous anti-corrosion agents comprising polycyclic hydrocarbons that have at least one anellated benzene ring, each having at least two ring-substituted hydroxyl groups in ortho position to each other. The aqueous anti-corrosion agent can be substantially free both of passivating chromium-containing compounds and of fluoride-containing compounds that pickle the metal substrate. Pre-treatment by drying (dry-in-place method) is especially advantageous. Accordingly, the method according to the invention is suitable in particular for the pre-treatment of metal strip, wherein excellent anti-corrosion results are achieved on surfaces of aluminum or steel. The invention further relates to a method for producing coated can lids from aluminum strip by using the previously mentioned zirconium-based anti-corrosion agent. A further aspect comprises an aqueous concentrate for providing the ready-to-use anti-corrosion agents.