Zina sins erase after marriage in islam?

I know it's a little too far-fetched to ume that after marriage, the sins of zina that you have committed with previous boyfriends are still there and not forgiven or pardoned unless you do tawba. But after marriage, do the sins of zina (adultery) that you have committed with your fiance (now husband) before marrying him pardoned or automatically erased now that the two of you are legally and islamically together anyway? Please support your answers with proof from the sharia (quran or sunna) or answer to the best of your knowledge if no proof exists..