The present disclosure provides a formulation and methods for simultaneously dissolving metal sulfide scales, inhibiting acid gas corrosion, and inhibiting the formation of calcite and barite in a system having low or high shear stress conditions due to fluid movement, in which the formulation contains a THP+salt, one or more corrosion inhibitors, one or more scale inhibitors, and one or more acid corrosion inhibitors. The formulation may be applied to the system in diluted or undiluted form, and continuously or in batch style.