You appear to be referring to Mass Disenchant. Firstly, are you using a translator? Salvage and Disenchant mean very different things.
Second: IMO, you should never use the Mass Disenchant function. Yes, its convenient, but its better to keep the extra cards in your collection, unless you really need the dust right now, in which case you should only disenchant as many cards as you need to. You can always disenchant more cards later.
Anyhoo, you seem to be concerned that Mass Disenchant will destroy golden copies rather than regular copies. However, before you hit the Mass Disenchant button, the game tells you exactly how many cards of each rarity AND quality you will destroy.
I just checked my Mass disenchant page which says I would destroy 1 normal legendary card, plenty of lower rarity normal cards but NO golden cards of any rarity.
I own every epic in Standard, and also have golden copies of some (due to the way duplicate protection works), but it appears that NO golden copies (of any rarity) would be destroyed. So, I’m pretty sure that golden copies are NOT destroyed by Mass Disenchant unless you have more than the maximum usable amount of GOLDEN copies.
I know that in the most recent expansion alone, I have FIVE golden epic cards where I also own 2 normal copies of the card: Window Shopper, Ensmallen, Mystery Egg, Wreck’em and Deck’em and Chemical Spill.
But as I said, my mass disenchant button would not destroy ANY golden cards, which therefore must include those 5 epics. However, I don’t know if it would destroy excess copies of the normal cards where I own golden copies.
Anyhoo, as I said earlier, I wouldn’t recommend using mass disenchant anyway, but its your call.
However, before you do so, I would ask yourself how much dust you would get, and more importantly, how much dust do you need to craft the cards you really want?
To find out, check your mass disenchant page. How many cards will be destroyed, and how many of them are golden?