Acidic Lubricant Coating for Metal Cold Forming
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Solution Overview
Problem
Conventional pretreatment methods for metal cold forming require multiple steps, involve alkaline lubricant compositions with short lifetimes, and often result in insufficient coating weights, leading to inadequate adhesion and friction reduction, and may cause cold welding.
Innovation Solution
A single-step method using an aqueous lubricant composition with a pH value below 2.0, containing oxalate anions, thiosulfate, chloride, film-forming polymers, wax, and fluoride anions, which serves as both a conversion coating and lubricant, eliminating the need for additional steps and rinsing, and providing a stable, long-lasting coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If multiple-step pretreatment methods with alkaline lubricant compositions are used, then coating coverage is achieved, but bath lifetimes are short and process complexity increases
Solution Approach 1:
The patent combines conversion coating and lubrication functions into a single aqueous acidic composition containing oxalate anions, thiosulfate anions, chloride anions, film-forming polymers, waxes, and fluoride anions. This eliminates the need for separate treatment steps and rinsing operations, extending bath lifetime while reducing process complexity.
Solution Approach 2:
The aqueous acidic lubricant composition performs multiple functions simultaneously: it acts as a conversion coating agent through oxalate and fluoride anions, provides lubrication through waxes and polymers, and ensures adequate adhesion and friction reduction. This multi-functionality resolves the contradiction by achieving comprehensive protection in a single step.
2Reliability
If conventional alkaline lubricant compositions are used, then lubrication is provided, but adhesion is insufficient and cold welding occurs
Solution Approach 1:
The invention uses a composite aqueous acidic composition containing multiple active components: oxalate anions for conversion coating, thiosulfate anions for enhanced adhesion, chloride anions for surface activation, film-forming polymers for binding, waxes for lubrication, and fluoride anions for corrosion protection. This composite formulation achieves superior adhesion and prevents cold welding through synergistic interactions.
Solution Approach 2:
The patent changes the pH parameter to acidic conditions (pH < 2.0) and adjusts the composition of active anions, which fundamentally alters the surface treatment mechanism. This enables simultaneous conversion coating and lubrication with excellent adhesion, preventing cold welding during cold forming operations.
3Productivity
If single-step acidic lubricant composition is used, then process simplicity and bath lifetime are improved, but coating weight homogeneity must be maintained
Solution Approach 1:
The patent ensures coating weight homogeneity by formulating the aqueous acidic composition with compatible components that dissolve and distribute uniformly. The oxalate, thiosulfate, chloride, polymer, wax, and fluoride components work synergistically to produce a homogeneous coating layer with consistent properties across the substrate surface.
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 achieves a high, homogeneous coating weight with excellent adhesion and friction reduction, preventing cold welding, and extends bath lifetimes, making it economically and ecologically advantageous.
Implementation Method 1
contacting the at least one surface of the substrate provided in step (1) with an aqueous lubricant composition (A) having a pH value below 2.0 and comprising besides water oxalate anions (a1), thiosulfate anions (a2), chloride anions (a3), at least one film-forming polymer (a4), at least one wax (a5), and fluoride anions and/or bifluoride anions (a6)
Data Source
AI summary
The present invention relates to method for pretreatment of a metallic substrate for a subsequent metal cold forming process, said method comprising at least steps (1) and (2) and optionally step (3), namely providing at least one substrate having at least one surface at least partially made of at least one metal (1), contacting the at least one surface of the substrate provided in step (1) with an aqueous lubricant composition (A) having a pH value below 2.0 and comprising besides water oxalate anions (a1), thiosulfate anions (a2), chloride anions (a3), at least one film-forming polymer (a4), which is a homopolymer and/or copolymer being prepared by polymerization of at least one ethylenically unsaturated monomer, at least one wax (a5), and fluoride anions and/or bifluoride anions (a6), and optionally drying the coating film obtained after having performed step (2), a pretreated metallic substrate obtainable by the aforementioned inventive method, a method of cold forming of a metallic substrate including a step of subjecting the inventive pretreated metallic substrate to a cold forming process, an aqueous lubricant composition (A) as defined above and a master batch for preparing the aqueous composition (A).