Plastic plating-Determination of surface brightness
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The brightness of the coating (also known as gloss) is an item that must be measured for plated parts with high decorative requirements. The brightness of the coating refers to the ratio and intensity of reflected light on the surface of the coating under the action of incident light at a certain illuminance and angle. The greater the ratio or intensity of reflected light, the higher the brightness of the coating. The brightness of the coating is mainly inspected and evaluated by visual inspection method and compared by template control method.
1. visual method
The visual method evaluates the brightness of the coating layer based on the experience accumulated by the inspector in practice and observes the light reflectivity of the coating surface. The brightness is divided into levels 1 to 4, with level 1 being the best. This method is usually used to test the light perception of most light industry daily products, and certain results are obtained.
The grading reference standards for the empirical evaluation method of visual brightness are as follows.
Level 1 (mirror brightness): The coating surface is as bright as a mirror, and facial features and eyebrows can be clearly seen.
Level 2 (brightness): The coating surface is bright, and facial features and eyebrows can be seen, but the eyebrows are cloudy.
Level 3 (semi-bright): The coating surface is slightly bright, and only the contours of facial features can be seen.
Level 4 (No shine): The coating is basically dull, and the contours of the facial features cannot be seen.
Since the evaluation by the empirical evaluation method is influenced by human factors and sometimes disputes the evaluation results, sealed samples can be used for comparison when necessary to serve as a reference for evaluation.
2. template comparison method
The template control method is actually an improvement of the visual inspection method and belongs to the comparative measurement method among the visual inspection methods. Because the template comparison method is to compare the specified standard brightness template and has a relative reference basis, it eliminates human disputes to a certain extent and improves the accuracy of the assessment.
1) Make standard brightness samples
(1) First-level brightness template: A copper (or iron) test piece with a roughness of 0.04μm<Ra<0.08μm after processing, plated with bright nickel and polished with chromium.
(2) Second-level brightness template: A copper (or iron) test piece with a roughness of 0.08μm<Ra<0.16μm has been processed and polished after electroplating bright nickel.
(3) Three-level brightness template: A copper (or iron) test piece with a roughness of 0.16 μm<Ra<0.32μm after processing, plated with bright nickel and polished with chromium.
(4) Fourth-level brightness template: A copper (or iron) test piece with a calibrated roughness of 0.32 μm<Ra<0.64μm after processing, plated with bright nickel and polished with chromium.
2) Inspection and evaluation methods
Under the specified test conditions (the same as the inspection surface defects), the plated part is repeatedly compared with a standard brightness template to observe the reflective performance of both. Finally, the reflective performance of the coating under inspection is similar to that of a standard template. When it is lower than a higher-level brightness template, the brightness level of the standard template is used as the brightness level of the coating under inspection.
3)precautions
(1)Standard brightness samples should be properly stored to prevent poor storage from changing the surface state.
(2)Before use, carefully wipe the standard template with a soft cleaning cloth to make its surface clean and show the specified reflective properties. When wiping, prevent damage to the standard state of the standard template.
(3)The service life of standard brightness samples is generally one year and should be updated regularly when used frequently.
3. The brightness meter measures the brightness of the coating
Since there is no strict standard for evaluating the brightness of the coating by visual inspection, and the observation varies from person to person, in recent years, foreign countries have reported using luminometers to measure the brightness of the coating, which can be used for planar plated parts to achieve better results.
