The evaluation of the performance of the chemical solution should refer to the provisions of the international standard GB 6807-86 "Technical Conditions for Phosphating Treatment of Iron and Steel Parts Before Embossing" and GB 11376-89 "Phosphate Conversion Coating of Metals". That is to say, it includes the appearance, thickness or weight of the chemical conversion coating, and the corrosion resistance after treatment. Depending on the special purpose, it is sometimes necessary to test the compatibility between the conversion film and the paint film layer, the hardness, friction coefficient, scratch resistance and other indicators of the conversion film. Regarding the three common indicators of the conversion coating, you can refer to the following standards and methods.
(1) Appearance
Using the visual method, the relevant standards GB 11376-89 "Phosphate Conversion Coating of Metals" and GB 6807-86 Technical Conditions for Phosphating Treatment of Iron and Steel Workpieces Before Painting.
(2) Thickness or film weight
The thickness of the film is measured by GB 6462 "Metal Oxidized Coating Layer Cross-Section Thickness Microscopic Measurement", and a Thickness Gauge can also be used in accordance with GB 4956 "Magnetic Method for Measuring the Thickness of Non-magnetic Coating Layers on Magnetic Metal Substrates" or GB 4957 "Non-magnetic Eddy current method for the measurement of non-conductive coatings on metallic substrates. Gravimetric method is used for film weight measurement, which can be in accordance with GB 6807 "Technical Conditions for Phosphating Treatment of Iron and Steel Workpieces Before Painting" or GB 9792 "Determination of Film Quality per Unit Area of Conversion Coating on Metal Materials".
(3) Corrosion resistance
The corrosion resistance of the phosphating film itself can be tested by copper sulfate drop method, sodium oxide salt water immersion method and salt spray test method. The spot method and salt water immersion method can be in accordance with GB 6807-86 "Technical Conditions for Phosphating Treatment of Iron and Steel Parts Before Painting". The salt spray test can be carried out in accordance with GB 1771-79 "Determination of Salt Spray Resistance of Paint Films" or GB 6458 "Neutral Salt Spray Test of Metal Coverings".
