Scrapdiver Serpent can't be blocked as long as defending player controls an artifact.
Smart artificers clean up after themselves.
Official Rulings for Scrapdiver Serpent
1/1/2011 : Whether Scrapdiver Serpent can be blocked is relevant only as the declare blockers step begins. If the defending player gains control of an artifact after Scrapdiver Serpent has become blocked, the Serpent will remain blocked.
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