question about chests

If I continue to open same chests(same map and need same key to open),probability that get gold weapon from chests is down like anti-farming code?

As far as I know, you have to do some seriously hardcore chest running to invoke the farming code. Like day and night chest runs hardcore. So... um... do something else once in a while and I think you'll be fine. The farming code covers repetative actions, so doing something random on occasion should hold it off.