Test the corrosion resistance of PVD vacuum coating
PVD coatings are used in many cases in corrosive environments, sometimes in contact with corrosive materials and media, and sometimes in corrosive atmospheres. For example, many plastic molds in contact with acidic plastic are highly corrosive (such as PVC, that is, polyvinyl chloride), if the car parts coating in the coastal or tropical areas after the work is more corrosive. Because of the ubiquitous corrosion potential, research, development and application of coatings must take into account their working environment, if there is a possibility of corrosion must do corrosion test.
Corrosion resistance test is the most common salt spray test, use common salt spray test chamber. Salt spray test chamber is by means of salt spray corrosion testing the reliability of the measured samples, salt fog refers to the atmosphere is made up of tiny droplets containing salt dispersion system, which is one of the artificial environment is three series, a lot of enterprise products to the surrounding ocean climate cause destructive to product, so the salt spray test chamber should to do. Salt spray test chamber can be divided into neutral salt fog and acidic salt fog. The difference lies in the different standards and test methods, also known as NSS and CASS test, which is the most common test method in artificial three-proofing climate. If do salt spray test, need in accordance with the relevant national standard (GB/T2423.17-2008).
PVD coating corrosion test is not mandatory national standards, just in order to master the coating corrosion resistance qualitatively, so in many cases does not necessarily salt spray experiment was carried out, can adjust measures to local conditions according to the existing corrosion test.For example, in order to study the corrosion resistance of composite coating (TiN+(Ti, Cr)N+Ti), electrochemical method was used to test it in a certain literature.Wear and corrosion experiments were carried out in 0. Lmol /L sodium chloride solution with Ag/AgCl as the reference electrode and platinum wire as the auxiliary electrode.EG&GPAR 273A potentiometer was connected with 1250Hz frequency conversion analyzer for data collection.Use a PMMA box with solution and transfer shaft, transfer shaft and friction sheet and motor connected.In addition, a movable rod supports the sample and the entire system applies a load to the friction plate.The position of the sample is adjustable for optimum test conditions.The sample to be tested shall be packed in a polyester resin with only the test portion exposed and the edges sealed to avoid cracking corrosion problems.The lead used for electrification shall also be placed in the resin and brazed on the back of the sample.Wear - corrosion test is plate - block form, friction plate rotation speed of 40rpm, load is 0.08 ~ 0.15kgf, friction plate is 43mm aluminum oxide plate or sodium calcium glass plate.The experimental period was 1h, and the cumulative wear route length was about 325m.Observe coating integrity by monitoring corrosion voltage;The polarization resistance is obtained by impedance spectroscopy.The weight loss value was obtained by analytical balance after the test.After the electrochemical test under wear condition, the samples were observed by optical instruments and scanning electron microscopy (SEM) to study the wear morphology.The following figure shows the measured wear and corrosion curve.
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