OCTG Threaded Connection Coating for White Rust and Galling Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Oil country tubular goods stored outdoors for long periods often experience white rust, leading to decreased galling resistance and sealability of threaded connections, which existing compositions and lubricant coatings fail to adequately address.
Innovation Solution
A threaded connection method involving a Zn—Ni alloy plating layer followed by a chromate coating, with specific conditions such as a stirring speed of 0.5 m/s or more, chromate treatment time less than 50 seconds, and drying temperature of 60° C. or less, to enhance corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy metal-containing compound greases are used to improve galling resistance, then galling resistance is improved, but environmental harm increases due to heavy metal contamination
Solution Approach 1:
The patent extracts and removes the harmful heavy metal components from the grease formulation while retaining the essential lubricating and anti-galling functions through alternative chemical compositions that are environmentally benign
Solution Approach 2:
The patent employs alternative grease compositions that, while potentially requiring more frequent application or having different service life characteristics, eliminate the need for environmentally harmful heavy metals, thus trading long-term environmental damage for shorter-term operational considerations
2Object-affected harmful factors
If grease-free threaded connections are used to eliminate heavy metal contamination, then environmental harm is reduced, but galling resistance deteriorates
Solution Approach 1:
The patent changes the chemical parameters and composition of the grease formulation, replacing heavy metal compounds with alternative substances that provide similar lubricating and protective functions without the harmful environmental effects, thereby maintaining galling resistance in an environmentally friendly manner
3Ease of manufacture
If conventional plating and coating methods are used on threaded connections, then manufacturing simplicity is maintained, but corrosion resistance deteriorates when stored outdoors for long periods
Solution Approach 1:
The patent employs composite plating and coating structures that combine multiple materials with complementary properties, creating a layered system that provides superior corrosion resistance while maintaining compatibility with existing manufacturing processes and overall structural integrity
4Reliability
If chromate treatment time is extended to improve corrosion resistance, then corrosion resistance is improved, but manufacturing time increases
Solution Approach 1:
The patent optimizes the chromate treatment parameters including time, temperature, and solution composition to achieve the required corrosion resistance with minimized treatment duration, balancing performance requirements with manufacturing efficiency
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 results in a threaded connection with excellent corrosion resistance, as evidenced by a white rust occurrence area ratio less than 50% after 300 hours of a salt spray test, maintaining galling resistance and sealability.
Implementation Method 1
a Zn—Ni alloy plating layer is formed on at least one of the pin-side contact surface and the box-side contact surface by electroplating
Implementation Method 2
a chromate coating is formed on the Zn—Ni alloy plating layer. The chromate coating formation step includes a chromate treatment step and a drying step after the chromate treatment step
Data Source
AI summary
This invention provides a threaded connection for oil country tubular goods that exhibits excellent corrosion resistance and galling resistance, and a method for producing the threaded connection for oil country tubular goods. The method includes a Zn—Ni alloy plating layer formation step of forming a Zn—Ni alloy plating layer, and a chromate coating formation step of forming a chromate coating after the Zn—Ni alloy plating layer formation step. The chromate coating formation step includes a chromate treatment step and a drying step. The chromate coating formation step satisfy one or more conditions selected from the following conditions 1 to 3.Condition 1: stirring speed of the chromating solution in the chromate treatment step: a linear speed of 0.5 m/s or more;Condition 2: chromate treatment time in the chromate treatment step: less than 50 seconds; andCondition 3: drying temperature in the drying step: 60° C. or less.