Text (5th+errata): {Tap}, Sacrifice ~this~: Put a +1/+1 counter on target nonartifact creature. That creature becomes an artifact in addition to its other types. [Oracle 2007/09/01]
The counter only gives the +1/+1. The artifactness is a permanent change not associated with the counter. [Aahz 1997/08/22] So if the counter is moved off of the creature the artifact nature stays.
