There is nothing I know of that can be applied on precious metals to
prevent scratches. Varnish may work as a temporary protective coat
while shipping… to be washed off before display, but careful
wrapping in soft tissue paper is much easier. Chrome plating comes to
mind but dismissed because it will cheapen white gold to the value of
That perfect polish you achieved on a new item is short lived.
Rubbing against cloth, paper and skin combined with normal
atmospheric dust will put on micro scratches. Careful handling is the
answer, some people wear a pair of white gloves while handling
precious items, and there are gloves made out of polishing cloth.