Intermediate Coating Layer for Oxide Adhesion
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Solution Overview
Problem
The formation of metal oxides on steel surfaces during the annealing process in hot-dip coating hinders proper wettability and leads to uncoated areas and poor adherence of subsequent metal coatings, requiring additional pickling steps that are difficult to control at an industrial scale, especially in high-strength steels with elements like Si, Mn, Al, and Cr.
Innovation Solution
A coated metallic substrate with a layer of oxides directly topped by an intermediate coating layer comprising Fe, Ni, Cr, and Ti, where Ti is above 5 wt.%, and the equation 8 wt.% < Cr + Ti < 40 wt.% is satisfied, which improves the adhesion of a subsequent anticorrosion metallic coating without the need for oxide removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the steel sheet is heated in a direct flame or radiant tube annealing furnace, then the steel sheet is annealed to prepare for coating, but metal oxides form on the surface which hinder proper wettability and cause uncoated areas
Solution Approach 1:
An intermediate coating layer comprising Fe, Ni, Cr and Ti (with Ti ≥ 5 wt.% and Cr + Ti between 8-40 wt.%) is introduced between the oxide layer and the anticorrosion coating. This intermediate layer acts as a mediator that adheres to both the oxide-containing steel surface and the anticorrosion coating, resolving the wettability problem without requiring oxide removal.
Solution Approach 2:
Instead of removing the harmful metal oxides formed during annealing, the invention accepts their presence and designs an intermediate coating layer that can adhere to the oxidized surface. The intermediate layer with specific composition (Fe, Ni, Cr, Ti) converts the harmful oxide layer into a viable substrate for coating application.
2Manufacturing precision
If pickling is performed to remove metal oxides before electro-deposition, then the surface is prepared for effective coating deposition, but the process becomes difficult to control at industrial scale
Solution Approach 1:
The intermediate coating layer serves as an intermediary that eliminates the need for pickling. It adheres directly to the oxide-containing surface and provides a suitable base for the anticorrosion coating, thereby simplifying the industrial process by removing the complex pickling step.
Solution Approach 2:
The invention changes the approach from surface preparation (oxide removal) to surface modification (adding intermediate layer). By changing the chemical composition and structure of the surface through the intermediate layer, the process becomes more controllable and suitable for industrial scale production.
3Reliability
If a conventional intermediate coating is applied over metal oxides, then coating coverage is improved, but adhesion remains poor and delamination occurs
Solution Approach 1:
The intermediate coating layer is designed as a composite material containing Fe, Ni, Cr and Ti in specific proportions (Ti ≥ 5 wt.%, Cr + Ti between 8-40 wt.%). This composite composition provides both coverage and strong adhesion to the oxide layer, preventing delamination while ensuring uniform coating distribution.
Solution Approach 2:
The specific compositional parameters of the intermediate layer (Ti content ≥ 5 wt.%, Cr + Ti between 8-40 wt.%) are optimized to achieve both good coverage and strong adhesion. By controlling these chemical parameters, the layer adheres firmly to the oxide surface while providing a suitable base for the anticorrosion coating.
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 intermediate coating layer enhances the adhesion of the anticorrosion coating, preventing delamination and ensuring uniform coverage, thus eliminating the need for oxide removal steps and improving the overall coating quality.
Implementation Method 1
the composition of which varies as a function of the final use of the steel sheet... can be applied using different coating technologies known to a person skilled in the art, such as, for example, vacuum deposition methods, hot-dip coating or electro-deposition
Implementation Method 2
an intermediate coating layer comprising Fe, Ni, Cr and Ti wherein the amount of Ti is above or equal to 5 wt. %... enhances the adhesion of the anticorrosion coating
Implementation Method 3
can be applied using different coating technologies known to a person skilled in the art, such as, for example, vacuum deposition methods
Implementation Method 4
The metal coating can also be applied by electro-deposition
Implementation Method 5
Annealing of the steel sheet as it passes through a furnace under an inert or reducing atmosphere to limit the oxidation of the surface of the sheet
Data Source
AI summary
A coated metallic substrate is provided, including, at least; one layer of oxides, such layer being directly topped by an intermediate coating layer comprising Fe, Ni, Cr and Ti wherein the amount of Ti is above or equal to 5 wt. % and wherein the following equation is satisfied: 8 wt. %<Cr+Ti<40 wt. %, the balance being Fe and Ni, such intermediate coating layer being directly topped by a coating layer being an anticorrosion metallic coating.