How to prevent oxidation of wire joint, copper wire and aluminum wire joint

How to prevent oxidation of wire joint, copper wire and aluminum wire joint

There are copper aluminum transition joints, direct connection and cable nose in the place where electrical materials are sold. You can go and have a look

Is it better to use aluminum wire or copper wire for rural wire and meter connection?
How many squares is better?

At present, the city and rural power departments are using aluminum wire into the home line, as for the line connected to the meter, the use of aluminum wire or copper wire, it depends on the number of household electrical equipment used; if the home load is not very large, the installation of aluminum wire is very economical

When electricians work, why can't they screw copper wire and aluminum wire together to connect the circuit
Answer with chemistry knowledge

Aluminum is an active substance. In the air, aluminum oxide is formed when encountering oxygen, which has poor conductivity. If copper wire and aluminum wire are twisted together, the conductivity will be reduced and the conductive effect of the line will be affected. Therefore, copper wire and aluminum wire cannot be twisted together