Except baptism doent cleanse us of our sins only the blood that Jesus shed on Calvary can do thay.
Baptism is like a marriage. When you accept Christ as your God, and say you accept him within you and will follow his voice, this is the ceremony that makes it legal. Next comes repentance of all our sin so Christ can make us his, and give us forgiveness. I think it is steps two and three when we teach a new convert.