Qinxiang Knowledge Booster – Is Your Metal Surface Clean?
The required degree of degreasing for the workpiece surface varies with and is determined by the subsequent operations after degreasing. The cleanliness of a workpiece can be described as a function that changes with the removal of specific surface contaminants, such as oil, grease, oxides, or particular soils.Methods for determining surface cleanliness range from primitive to highly sophisticated. Below are some testing methods compiled by Qinxiang New Materials:
Water Break Test:
The water break test checks for the presence of a continuous water film on the surface without any breaks. If the water film remains continuous and unbroken, it indicates the absence of hydrophobic surface contaminants. Oil, grease, and insoluble organic substances are examples of hydrophobic contaminants. The water break test cannot indicate the presence of hydrophilic contaminants or oxides.
White Glove Test:
The white glove test is used to check for the presence of particles on the surface after degreasing and, to a certain extent, for the presence of organic contaminants. The test can be performed while the workpiece is still wet after rinsing or after it has dried. The surface of the workpiece to be tested is wiped with a white glove, cotton, or lens paper, and then the material used for wiping the surface is examined for the presence of black, gray, off-white residues, or oily dirt.
If contaminants are found, further examination under a microscope or advanced chemical or surface analysis is performed on the workpiece surface or the material used for wiping to determine the nature of the contaminants.
Other Methods:
Complex physical and chemical analysis methods can be used to test the residual contaminants on degreased surfaces. Degreased and dried test specimens are immersed in a turbulent solvent solution to analyze for organic contaminants and insoluble particles. The amount of contaminants found in the solvent indicates the degree of degreasing.
• The surface of degreased workpieces needs to undergo special analysis to determine the presence of oxides, organic substances, and particulate contaminants. In strict degreasing operations, allowable contaminants and their concentrations must be controlled.
• Analytical techniques such as infrared microprofilometry (developed by Sandia National Laboratories), X-ray photoelectron spectroscopy (Oak Ridge National Laboratory), and optical reflectance technology (Dow Chemical Company) have been used to analyze residual soils in critical degreasing operations.
• If the soil is doped with a substance that can fluoresce, the degreased workpiece is exposed to ultraviolet light to confirm the presence of any residues.
• Methods for testing surface cleanliness based on the measurement of surface tension have been put into use. Care must be taken to use test liquids specific to the substrate surface.
This concludes Qinxiang New Materials' introduction to metal surface cleaning. For more information on raw materials for metal hard surface cleaning, please feel free to contact us.~