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Inspection standard for surface treatment of thick-walled stainless steel pipes

Surface cleanliness generally refers to the degree of cleanliness of the desired surface after degreasing, descaling, descaling and other corrosion products, removal of old coatings, and even the processing of polishing and polishing of thick-walled stainless steel pipes. At present, there are mainly the following methods for judging surface cleanliness:


Visual inspection, this is the most important and simple way to judge the cleanliness of the entire thick-walled stainless steel pipe surface. It is used to check all visible contaminants. This type of visual inspection does not require an auxiliary optical instrument such as a magnifying glass. In the fluorescence test, various lipid contaminants can be seen very clearly using ultraviolet rays. Wipe test for partial inspection of visible contaminants. White or black linen and filter paper can be used as inspection supplies. Check that the skin is not in contact with the surface being inspected and that the linen fibers are not left on the surface. When the surface is rough, wipe it gently. If the linen is discolored or a reflection change occurs on the rubbed surface or a wiping mark is left, the deletion indicates that the surface is dirty. In the nail test, contaminants with poor adhesion and visible can be removed by nails.


pH test paper inspection, pH test can be used to check whether the surface remains acid or alkali. When the pH is <6.4, the blue litmus paper turns red; when the pH is <8.3, the red snapper to the vine paper turns blue. Measure the relative humidity and measure the atmospheric conditions to determine whether the surface is visible or invisible to the surface. The accurate measurement can only be done with a hygrometer (dry to wet hygrometer).


Water infiltration test to check for the presence of oil film. This method uses water to infiltrate the oil to spray water onto the metal surface. If there is no oil, the water film is completely continuous and does not form water droplets; if there is oil on the surface, the water film is interrupted and broken, and water droplets are formed from oil stains. Roll up. A solution containing 0.1% red dye may also be applied to the surface to be tested; if the droplets spread around and form a circular boundary, the surface is relatively clean. Conversely, if the droplet does not expand significantly, it will leave a zigzag boundary, which is a symbol of oil on the surface. It should be noted that the dirt contaminated on the metal surface is sometimes a hydrophilic substance. In order to avoid inaccurate testing, it may be immersed in dilute sulfuric acid before the final cleaning to observe the wet film on the metal surface.




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