Overview
Metal processed parts use machining oils and release agents during the manufacturing process. These oils must be removed through cleaning processes as they can cause defects in subsequent processes such as coating and plating. This article introduces various methods and principles for evaluating cleaning effectiveness.
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Purpose of Cleaning Metal Processed Parts
Oil Adhesion During Metal Processing
Metals come into contact with various oils during processing. These include machine lubricants, processing oils, and rust preventive oils that adhere to metal parts for various reasons and purposes.
Main Purpose is Degreasing
These oil residues can repel coating agents or plating in subsequent processes, leading to defects. Therefore, oil removal is essential in metal processing. This oil removal process is called "degreasing."
Introduction to Degreasing Methods (Physical and Chemical)
There are two main degreasing methods:
１．Physical Degreasing Methods
・Wiping with cloth・Dry heating in high-temperature furnaces for several hours to oxidize and burn off oil
２．Chemical Degreasing Methods
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- Previously used chlorinated and fluorocarbon solvents (now restricted due to health and environmental concerns)
- Currently using environmentally friendly cleaners like hydrocarbon cleaning fluids and alkaline cleaning solutions
Oil Residue Testing Methods
Why Perform Oil Residue Testing
Manufacturing facilities need to verify cleaning effectiveness to manage product quality. Insufficient verification can lead to:
- Undetected product oil residue
- Defects in subsequent processes
- Time-consuming process improvements
Six Testing Methods Used in Manufacturing
１．Simple Wettability Test (India Ink)
Apply or immerse sample in India inkWell-degreased surfaces show uniform ink coverage
Poor cleaning shows ink repulsion in areas with remaining oil
2.Reagent Wettability Test (Dyne Pens)
More quantitative than India inkUses pens with different surface tension values
Determines surface energy through ink behavior
3.Visual Inspection with Light
Uses black light inspectionFluorescent substances in processing oils become visible
Simple visual confirmation method
4.Adhesion Tape Test
Apply cellophane tape to cleaned surfaceApply pressure and perform peel test
Poor cleaning shows tape peeling
5.Contact Angle Measurement
Quantitative wettability measurementMeasures angle between water droplet and surface
Smaller angles indicate better cleaning
Can calculate surface energy using Young's equation
6.Residue Analysis (Infrared Spectroscopy)
Quantitative measurement of surface oilUses Lambert-Beer law
Measures absorbance of extracted oil
Compares results with calibration curve
This translation maintains the technical accuracy while making the content accessible to English readers. The structure and key points of the original article are preserved while ensuring natural English expression.
