Under the action of arc, silicon compounds easily generate insulating substances, which reduces the voltage. Therefore, silicone grease is generally not used for high current contacts. In contrast, the tiny current contacts use a lot of silicone grease. This is because the tiny current contacts do not generate arcs, and the viscosity of silicone oil changes little with temperature, and the temperature range that forms an appropriate oil film thickness is wide, making it difficult to produce intermittent electric shocks at low temperatures. In addition, silicone grease has poor lubricity, causing the contact surface to become rough due to wear, which can prevent the transfer to fluid lubrication and reduce intermittent electric shock.
Using electrical contact grease can reduce the occurrence of arcs, reduce electrical corrosion and wear, and avoid contact failure. The arc temperature generated by high current is very high, even high enough to decompose any organic molecules. Therefore, high current contact grease generally uses synthetic polyether as the base oil that can completely burn cleanly without leaving any residual carbon.
3. Lubrication and anti-wear, extending contact life
Use electrical contact grease to eliminate noise and reduce wear. This is especially important for electrical contacts that are plated with precious metals such as gold. Reduced wear can allow the plating to be thinned, greatly reducing costs. Electrical contact grease improves the lubrication performance between contact elements, avoids mechanical wear of the contacts, and extends the service life of the electrical contacts.
4. Anti-sulfurization of silver contacts
According to the requirements of electrical conductivity, most of the small current contacts use silver, which has the lowest resistance among metal materials. The disadvantage of silver is that it is prone to sulfide corrosion, and even trace amounts of sulfur-containing gases present in the atmosphere will cause damage to it. The formation of sulfide film is the cause of poor contact. Therefore, the grease for small current contacts must have the ability to protect the silver surface from sulfur-containing gases, that is, it must have anti-sulfide properties. Since silver contacts are susceptible to vulcanization, a sulfur-free grease must be used.
Selection of electrical contact grease
1. Oil film strength, appropriate high and low temperature range, and ability to stay in a fixed position. Its special feature is that it must be able to avoid wear and tear.
2. Low-viscosity base oil should be used for switches with low current/low contact force.
3. High-viscosity base oil should be used for switches with high current/high contact force.
＜1A ------- low current;
1-10A ------- medium current;
＞10A-- ----- Large current;
The greater the current, the greater the spark generated, so a larger base oil viscosity needs to be selected.