Influence Of Particle Corrosion On Performance Of Electrical Contact

Through numerous analyses of the failure contacts, the main effect factors on performance of electrical contact are materials, manufacture, and environmental pollution and so on. The environmental pollution is very serious in China, and the contact surfaces are usually exposed in atmosphere without any protection, so environmental pollution is one of primary reasons that cause the failure of electric contacts.The previous study of our research lab of electric contacts shows that a mass of corrosion contamination was found on the electric contact surfaces and dust often accompanies with it. The salt that exists in the dust particles is the inherent factor of the corrosion. Different varieties of ion have different corrosion behavior. On the other hand, the salt corrosion will be different in different temperature and humidity, so it's necessary to study the particle corrosion on performance of electrical contact materials by the experiment of special salt particle corrosion in dust on electrical contact materials. Salt corrosion will influence the dust particle's staying on contact surface, and the degree of the trap will influence the contact reliability, so it is very important to study it. It is necessary to set up a lab simulation method which is fit for dust particle corrosion.In this thesis, the following experiments were carried out. First, corrosion behavior of Na2SO4 particles and NaCl particles on gold plating sample and copper sample under specified temperature and humidity conditions; Second, compressive strength of the two kinds of particles; Third, preliminary study of the lab simulation method on the particle corrosion; And finally, preliminary study on the trapping effect of the corrosion on dust particle on the contact surface. The compressive strength of the Na2SO4 particles is much less than NaCl particles. The corrosion of the Na2SO4 particles is far below the NaCl particles. The reason is that the hardness of the sulfate ion SO42- is harder than chlorine ion Cl", and the sulfate ion is bigger than the chlorine ion and has not penetrability. The corrosion of the chlorine ion is far below the natural dust particle. This is because the NaCl solution is neutral, and the natural dust particle solution is faintly acid. The effect factor of the particle corrosion is complicated, so we should not only think of the composition and the solution of the salt, but also think of the pH of the particle.It is necessary to add NaCl particle in the lab accelerated simulation of the dust corrosion, and when dipping the sample into the NaCl solution, the corrosion is clearer than when dripping NaCl solution on the sample. The corrosion of the particle is not aggravated when adding concentrated sulfuric acid to the calcium carbonate solution.SiO2 particles on the contact surface will be pushed away from the contact area only in few fretting cycles'motion, and it will decrease the contact failure probability. After humidity experiment, SiO2 particle will not stay on the contact surface longer. SiO2 particles will stay on the contact surface longer when there is corrosion product wrapping up them. It takes dozens of times of fretting cycles to push SiO2 particles away from the contact area. In the heavy pollution environment, because of the trapping of the corrosion on the contact surface, the dust particle stay on the contact surface longer, and it will need hundreds of fretting cycle to push the dust particle out of the contact area.