Caig Labs DeoxIt product is excellent for oxidized switch contacts. I don't
use abrasives on any contacts (motor or relay contacts, or electronics
switches) because it degrades the surfaces.
I typically use a heavy paper such as file folder strips wetted with DeoxIt
to clean contacts.
Where the contacts are slightly rough or badly oxidized (or dirty) I'll use
the end grain of a hardwood swab stick or a pop-cicle stick cut with a long
tapered bevel.

Badly pitted contacts require replacement, particularly where they carry
larger currents in power applications. I don't put much trust in sandpapered
contacts, as they're reliability is questionable, likely to fail in ways
that could cause other problems.

Cheers
WB
..................

"Eric" wrote in message
...
Most of the old equipment has power supply switch problem. The contacts
arc
by electric power and need to be replaced or sand down to refinish the
surfaces to prevent resistance build up. After the resurfacing surface,
is
there any chemical can prevent the arc again and the oxidation coming
back?
I am using the de-ox cleaner now, any other suggestions.

Thanks

Eric