D1 filter paper method
D1.1 Application scope
This method is capable of measuring macroscopic porosity in regular or uncracked chrome layers that access the substrate.
D1.2 Test solution
D1.3 Test procedure
The test environment should be kept clean to avoid dust such as iron and copper in the air.
Use ethanol or other appropriate degreasing agents to effectively remove oil stains on the surface to be tested, rinse with distilled water and dry.
Stick the filter paper soaked in the above solution (see D1.2) tightly on the surface to be tested for 10min. If the filter paper is dry during this period, use a little test solution to wet the filter paper.
Remove the filter paper and observe the surface of the contact angle with the coating. The blue marks indicate that there are pores on the coating that can reach the steel substrate; the reddish-brown marks indicate that there are pores that can reach the copper or copper alloy substrate.
D1.4 Record the test area and the number of imprints, measure the porosity according to the regulations, the unit is points/cm2, measure and record the size and quantity of the largest imprint or other phenomena observed if necessary.
Note: The porosity measurement method stipulated in some foreign engineering chromium standards uses different components or different potassium ferricyanide contents, or adopts different test procedures. There are often large differences between the test results of these methods and the test results of Chapter D1.
D2 visual inspection
D2.1 This method cannot be used for the determination of pores or cracks in conventional chromium layers
D2.2 Under an optical microscope with a magnification of 100, use reflected light to inspect the cracks on the surface of the chromium layer. When counting very fine cracks accurately, a higher magnification may be required. To make the count more accurate, use a micrometer eyepiece or A similar device can measure the number of cracks along a certain length.
Adjust the magnification of the microscope to select a measurement length at which at least 40 cracks can be counted in the field of view.
D3 Electrodeposited Copper Measurement Method
D3.1 This method is generally used to measure the pores or cracks of the chromium layer when nickel is used as the bottom layer. It can quickly visually detect the uniformity of pores and cracks. If counting is required, it should be carried out according to the provisions of D2.2.
D3.2 Principle
In an acid copper sulfate solution, a copper layer is electrodeposited on the surface of the chromium plating layer at a low current, and the copper is deposited only on the bottom layer where cracks, holes and other discontinuities of the chromium layer are exposed.
D3.3 Operation steps
The copper plating effect is the best immediately after the sample is electroplated with chromium, otherwise the sample should be effectively degreased. Any electrolytic treatment should be avoided, and degreasing methods such as ultrasonic cleaning or magnesium oxide powder water slurry brushing can be used.
If copper plating is carried out a few days after electrochrome plating, the sample should be immersed in 10~20g/L nitric acid for 4min before copper plating after degreasing, and the solution temperature is 95°C, which will help to reveal cracks or pores.
