This document provides guidelines and describes quality control and testing procedures for application of either stainless steel or nickel-base corrosion-resistant weld metal overlay (hereafter referred to as CRO) on internal surfaces in continuous digesters, impregnation vessels, and batch digesters in kraft and soda service. These guidelines provide information concerning overlay properties and application procedures that affect the performance of the overlay.

The scope for CRO in digester vessels should specify the:
• Area to be overlaid.
• Welding materials to be used.
• Surface preparation.
• Criteria for determining where buildup or repair of the substrate is necessary, and procedures for making this decision.
• Jurisdictional regulations and applicable Codes with which to comply.
• Procedure documentation.
• Work-product documentation.
• Quality control and testing plan.
• Safety and job support requirements (scaffolding, ventilation, power supply).