Zn-Ni Thread Coating With Solid Lubricant for Galling Resistance
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Solution Overview
Problem
Existing coatings for tubular threaded elements in oil and gas applications suffer from issues such as galling, corrosion, delamination, and increased screwing torque due to environmental exposure and repeated use, leading to potential leakage and inefficiencies in connections.
Innovation Solution
A multilayer coating comprising a zinc-nickel first layer, an oxalation-type conversion layer, and a polyurethane or epoxy matrix with solid lubricant particles, providing improved lubrication, corrosion resistance, and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid depositions (metal coatings) are used to prevent galling and provide anti-corrosive properties, then lubrication and corrosion resistance are improved, but the deposition itself becomes subject to corrosion and delamination in aggressive environments
Solution Approach 1:
The patent applies a composite material structure consisting of a zinc-nickel alloy deposition combined with an organic coating layer. This composite structure allows the inorganic zinc-nickel layer to provide corrosion resistance and solid lubrication, while the organic coating layer protects the deposition from corrosion and prevents delamination in aggressive environments. The combination of different material properties in a single coating system resolves the contradiction between providing protective functions and maintaining deposition stability.
2Ease of operation
If greases are applied to threaded areas to reduce galling and facilitate screwing operations, then lubrication is improved, but the grease is extruded from components and released into the environment causing blockages
Solution Approach 1:
The patent replaces traditional greases with a solid lubricant system based on zinc-nickel deposition with an organic coating. This solid lubricant system provides the necessary lubrication for screwing operations without the drawbacks of grease extrusion and environmental pollution. The solid coating remains in place on the threaded components, providing continuous lubrication without being displaced into the environment.
Solution Approach 2:
The patent substitutes a mechanical/chemical lubrication system (grease) with a solid surface engineering solution (electrodeposited zinc-nickel alloy with organic coating). This replacement eliminates the need for bulk lubricant application while providing equivalent or superior lubrication performance through the solid coating surface, thereby preventing environmental contamination.
3Strength
If high axial loads are applied during screwing operations to couple tubular elements, then connection strength is improved, but galling occurs in threaded areas and metal/metal sealing surfaces
Solution Approach 1:
The patent changes the surface properties of the threaded components by applying a zinc-nickel deposition with controlled composition (containing 8-12% nickel) and surface characteristics. This parameter change in the surface material properties provides both the strength to withstand high axial loads and the lubrication characteristics to prevent galling, allowing the connection to achieve both objectives simultaneously.
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 multilayer coating significantly reduces galling and corrosion, maintains lubrication effectiveness over time, and stabilizes the connection, ensuring reliable screwing and unscrewing operations with reduced torque and enhanced endurance.
Implementation Method 1
a first layer (11) of a solid coating comprising Zinc-Nickel electrodeposited on said at least one portion of the surface of the threaded end (3)
Implementation Method 2
a second layer (12) of a conversion layer of the oxalation type above the first layer (11)
Implementation Method 3
a third layer (13) comprising a polyurethane or epoxy matrix loaded with solid lubricant particles above the second layer (12)
Data Source
AI summary
A tubular threaded element for the drilling, the operation of hydrocarbon wells, the transport of oil and gas, the transport or the storage of hydrogen, the carbon capture or the geothermal energy, including a metal body and at least one threaded end including at least one threaded portion, the threaded end including a multilayer coating on at least one portion of the surface of the threaded end wherein the multilayer coating includes a first layer including a solid coating including Zinc-Nickel electrodeposited on the at least one portion of the surface of the threaded end, a second oxalation-type conversion layer above the first layer, a third layer including a polyurethane or epoxy matrix loaded with solid lubricant particles above the second layer.