Steel Pipe Anti-Corrosion Coating System
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Solution Overview
Problem
Existing coatings for steel pipes do not provide strong adhesion to withstand pressure drops in oil and gas production pipelines nor are they impermeable to both liquids and gases simultaneously.
Innovation Solution
A thermoplastic coating system comprising a layer of epoxy resin with free hydroxyl groups, a thermoplastic adhesive layer of anhydride modified polyolefin or acrylic acid modified polyolefin, and a layer of 12-Aminododecanoic acid lactam, applied with a procedure that includes heating the steel pipe to achieve full adherence and impermeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coatings (cement mortar, plastic liners, epoxy) are applied to steel pipes, then corrosion protection is achieved, but adhesion strength is insufficient to withstand pressure drops in oil and gas pipelines
Solution Approach 1:
The invention applies a multi-layer composite coating system consisting of: (1) epoxy resin layer with free hydroxyl groups providing corrosion protection and chemical bonding to steel, (2) thermoplastic adhesive layer (anhydride modified polyolefin or acrylic acid modified polyolefin) providing mechanical adhesion strength, and (3) plastic pipe layer providing structural integrity. This composite structure combines the advantages of each material to achieve both corrosion resistance and high adhesion strength capable of withstanding pressure drops.
Solution Approach 2:
The thermoplastic adhesive layer acts as an intermediary between the epoxy resin layer and the plastic pipe layer, ensuring strong bonding between these two components. The adhesive layer contains functional groups that can bond with both the epoxy hydroxyl groups and the plastic pipe material, creating a reliable transition zone that transfers and distributes mechanical stresses, thereby preventing delamination under pressure drop conditions.
2Reliability
If conventional coatings are applied to steel pipes, then some impermeability is achieved, but simultaneous impermeability to both liquids and gases is not achieved
Solution Approach 1:
The multi-layer composite coating system addresses the impermeability challenge by combining materials with complementary properties. The epoxy resin layer provides barrier properties against liquids and chemicals, while the thermoplastic adhesive layer and plastic pipe layer provide additional barrier properties against both liquids and gases. The layered structure creates multiple tortuous paths for penetrants, significantly reducing permeability to both liquid and gas phases simultaneously.
Solution Approach 2:
Each layer in the composite coating is designed with specific local qualities optimized for its function. The epoxy layer is formulated with specific hydroxyl group content and crosslinking density for liquid barrier properties, while the thermoplastic adhesive layer is designed with appropriate molecular weight and crystallinity for gas barrier properties. This localized optimization of material properties in different layers achieves comprehensive impermeability.
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 coating system achieves strong adhesion to withstand pressure drops and is impermeable to liquids and gases, maintaining integrity across a range of temperatures and pressures.
Implementation Method 1
a layer of thermoplastic adhesive applied directly onto the layer of epoxy resin
Implementation Method 2
a procedure that includes heating the steel pipe to achieve full adherence
Implementation Method 3
applying heat at a temperature higher than the point of softening of the thermoplastic material
Data Source
AI summary
The present invention includes an inner anticorrosive and abrasive resistant coating (10) for steel pipes (1) used for the transport of fluids. The coating includes: a layer of epoxy resin (2) having free hydroxyl groups, which are applied directly to the inside 1a of the steel pipe (1); a layer of thermoplastic adhesive (3) applied directly onto the layer of epoxy resin; and a layer of 12-Aminododecanoic acid lactam with the formula (C12H23NO), which is applied directly onto the layer of adhesive.