A down-hole treatment tool including a tool body having a bore therethrough, a treatment port orifice disposed on the body, a sliding sleeve within the bore of the body. A constant-volume annular chamber, in isolation from the inner bore and the environment outside the body, provides a debris-free environment for locking the sleeve. A dissolvable treatment port cover provides protection of the treatment port until operation of the treatment port is needed. The treatment port cover and lubrication ports enable lubrication of the sleeve and inner bore of the body without risk of contamination by debris.