Photocurable Coating for Steel Pipe Threaded Joints
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Solution Overview
Problem
Existing coatings for threaded joints in steel pipes, particularly those used in oil country tubular goods, face challenges such as the need for compound grease which poses environmental and health risks, lack of transparency for visual inspection, and inadequate corrosion resistance and adhesion in extreme temperature environments.
Innovation Solution
A photocurable composition comprising a (meth)acrylate resin, (meth)acrylate monomers, a photopolymerization initiator, benzotriazole anticorrosive agent, anticorrosive pigment, and phosphate ester, which forms a transparent, corrosion-resistant, and adhesive photocured coating when cured with active energy rays, eliminating the need for compound grease and enhancing galling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compound grease is applied to the contact surfaces of a threaded joint, then galling resistance and gastightness are improved, but environmental and health hazards increase due to heavy metal powders
Solution Approach 1:
The invention extracts and removes the harmful heavy metal powders (zinc, lead, copper) from the lubricant composition while retaining the essential lubricating and protective functions. The photocurable composition uses organic compounds instead of inorganic heavy metals, eliminating environmental and health hazards associated with compound grease.
Solution Approach 2:
The invention changes the chemical composition parameters from traditional compound grease containing heavy metals to a photocurable composition with organic lubricants and anticorrosive agents. This parameter change maintains lubricating properties while eliminating harmful substances, allowing the coating to cure upon light irradiation and form a protective layer without toxic components.
2Reliability
If a coating is applied to the threaded joint, then corrosion resistance is improved, but visual inspection becomes difficult due to lack of transparency
Solution Approach 1:
The invention applies local quality by making the coating transparent in regions requiring visual inspection while maintaining protective properties throughout. The photocured coating allows light transmission, enabling inspection of the threaded portion underneath without removing the coating, thus achieving both corrosion protection and inspectability simultaneously.
3Ease of operation
If compound grease is used for lubrication, then lubricating properties are improved, but the work environment and human health are adversely affected by toxic effects
Solution Approach 1:
The invention converts the harmful compound grease into a beneficial photocurable coating system that cures upon light exposure. The uncured composition provides lubrication during application, and after curing, it forms a protective, non-toxic layer that eliminates ongoing health hazards while maintaining lubricating properties through the photocured film.
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 photocured coating provides excellent gastightness, adhesion, lubricating properties, and corrosion resistance, allowing for visual inspection without removing the coating and maintaining performance in extreme temperature conditions, reducing environmental and health hazards associated with compound grease.
Implementation Method 1
a photocurable composition which comprises (A) a photocurable (meth)acrylate resin, (B) a (meth)acrylate monomer selected from a monofunctional (meth)acrylate monomer and a difunctional (meth)acrylate monomer, (C) a trifunctional or higher multifunctional (meth)acrylate monomer, (D) a photopolymerization initiator
Implementation Method 2
a photocurable composition which comprises (E) a benzotriazole anticorrosive agent, (F) an anticorrosive pigment selected from a phosphate anticorrosive pigment and calcium ion-exchanged silica
Implementation Method 3
a photocurable composition which comprises (G) a phosphate ester
Data Source
Figure 1
AI summary
A thin and highly transparent coating having excellent air tightness, adhesion to a substrate, lubricating properties, galling resistance, and corrosion resistance is formed on the surface of a metal substrate and particularly on the surface of a threaded joint which is used for connection of oil country tubular goods. A photocurable composition comprising (A) a photocurable (meth)acrylate resin, (B) a (meth)acrylate monomer selected from a monofunctional (meth)acrylate monomer and a difunctional (meth)acrylate monomer, (C) a trifunctional or higher multifunctional (meth)acrylate monomer, (D) a photopolymerization initiator, (E) a benzotriazole anticorrosive agent, (F) an anticorrosive pigment selected from a phosphate anticorrosive pigment and calcium ion-exchanged silica, and (G) a phosphate ester is used to form a photocured coating.