Design, Fabrication, and Surface Finish Practices for Tanks and Vessels to Be Lined for Immersion Service – NACE SP0178
Definitions
Surface Finish: The degree of smoothness of a surface produced by the removal of sharp edges and the appropriate surface preparation of welds and other rough areas. The term surface finish is also used to characterize the degree of smoothness that is necessary to attain a surface to which the lining can be applied satisfactorily in accordance with the lining specification.
Surface Finish Practices
Sharp edges shall be ground to a smooth radius of at least 3.2 mm (0.13 in.) or as agreed between the tank or vessel fabricator, tank or vessel owner, and lining applicator.
All rough welds shall be ground to remove sharp edges and other such irregularities (see Figure A2, Appendix A).
Appendix C – Written and Graphic Descriptions of Various Degrees of Surface Finishing of Welds That May Be Specified in Preparation for Lining of Tanks and Vessels (A)
| NACE Weld Preparation Designation | Type of Grinding | Butt Weld |
| A | Ground flush and smooth; free of all defects. (B) | Weld spatter is removed, and all surface imperfections are repaired as necessary. The weld is ground flush with the plate surface. |
| B | Ground flush | Minor Imperfections such as porosity and undercutting exist. The weld is ground flush with the plate surface. |
| C | Ground smooth; free of all defects. (B) | Weld spatter is removed, and all surface imperfections are repaired as necessary. The weld is ground smooth and blended into the plate surfaces. |
| D | Ground smooth and blended. (B) | Minor imperfections such as porosity and undercutting exist. Weld spatter is removed; Welds are then ground smooth and blended into the plate surfaces. |
| E | Minimal | Sharp projections on the weld bead, slag, and weld spatter are removed. |
(A) The written descriptions of the various degrees of surface preparation of welds in the appendices of this standard take precedence over the graphics and the companion visual comparator. The graphics are only pictorial representations of welds and grinding finishes and are not intended to be representative of the integrity of the welds. The “weld condition prior to finishing” is not a typical weld; it is only Intended to illustrate defects in welds that must be corrected prior to lining. Good welding practices and welding codes govern the integrity of the tank and vessel welds; this standard only addresses surface preparation of the welds tor the purpose of lining the tank or vessel for immersion service.
(B) Abrasive blasting in preparation for coating may reveal additional porosity and undercutting. Some applicators request the fabrication to blast the welds to reveal these imperfections prior to requesting inspection of the grinding by the lining applicator. Responsibility for repair of Imperfections so revealed should be resolved in the pre-job conference.
The visual comparator mentioned In Appendix C is a molded plastic replica that illustrates various degrees of surface finishing for welds prior to coating and lining. Full-seam welds, skip welds, butt welds, and lap welds, and others are depicted. For more information, contact the NACE International, https://www.nace.org
Coating Steel Water-Storage Tanks – AWWA D102
The purpose of this standard is to provide the minimum requirements for coating steel water-storage tanks, including materials, coating systems, surface preparation, application, and inspection and testing.
Inside Coating Systems
| System | Primer | Intermediate | Finish | Total |
| ICS-1 | 3.0 | 5.0 | 8.0 | |
| ICS-2 | 3.0 | 4.0 | 5.0 | 12.0 |
| ICS-3 | 2.0 | 4.0 | 4.0 | 10.0 |
| inside coating system No. 3 (ICS-3) has been changed to represent a one-coat or two-coat system, consisting of an optional two-component epoxy primer or inorganic or organic zinc-rich primer and a two-component epoxy topcoat, and the epoxy topcoat reflects a minimum volume solids content of 96 percent (see Sec. 4.4.4.) | ||||
| ICS-4 | 25.0 | |||
| This is a thermoset polymer that is the reaction product of a polyisocyanate resin that includes both 100 percent solids polyurethane and/or polyurea technologies. | ||||
| ICS-5 | 2.0 | 4.0 | 4.0 | 10.0 |
Cathodic Protection System Considerations
When an impressed current cathodic protection system is installed, it is recommended that the system not be energized until after the first anniversary inspection. When a sacrificial cathodic protection system is used, it is recommended that the anodes not be activated until after the first anniversary inspection. This is recommended to rule out the possibility that the cathodic protection system could be responsible for coating system defects discovered during the first anniversary inspection.
NACE TM0115 Cathodic Disbondment Test for Coated Steel Structures under Cathodic Protection
This NACE International standard test method specifies procedures to evaluate cathodic disbondment resistance of the steel structure coating systems under cathodic protection, such as buried or submerged pipeline and tank linings. The standard covers all test specimen geometries and test temperatures. This standard also takes into consideration all test parameters with the goal of the standard to be used during the selection of protective coating systems for use under cathodic protection. This test method is intended for use by facility owners, coating applicators, and coating manufacturers. Key words: buried service, cathodic disbondment, cathodic protection, coatings, immersion service, linings, pipelines, tanks, steel structures, test method
NACE RP0388 Impressed Current Cathodic Protection of Internal Submerged Surfaces of Steel Water Storage Tanks
This recommended practice presents accepted procedures for applying impressed current cathodic protection to the internal submerged surfaces of steel tanks used for the storage of natural waters.
NACE RP0196 Galvanic Anode Cathodic Protection of Internal Submerged Surfaces of Steel Water Storage Tanks
The purpose of this standard recommended practice is to present the procedures and practices used in providing galvanic anode cathodic protection to the normally submerged steel surfaces inside water storage tanks. This standard provides owners, engineers, and contractors with specific guidelines for the design and installation of these cathodic protection systems; methods for determining the effectiveness of these systems; and recommendations for the operation and maintenance of these systems. This standard is applicable to water storage tanks of various sizes used in municipal water supply and fire protection, including elevated tanks as well as flat-bottom tanks at ground level. Although the general principles outlined in this standard are applicable to all such tanks, the galvanic anode cathodic protection system described in this standard may not be practical for relatively large tanks.