scope:

FOREWORD

This SSPC/NACE joint standard defines the process for preparing a carbon steel surface to the Near-White Metal degree of surface cleanliness using a wet abrasive blast (WAB) method of cleaning. This standard is intended for use by coating or lining specifiers, applicators, inspectors, or others whose responsibility is to define a standard degree of surface cleanliness for carbon steel surfaces to be achieved by wet abrasive blast cleaning.

WAB cleaning is a process using a mixture of water and abrasive that can produce various levels of surface cleanliness and surface profile (roughness) similar to those obtained with dry abrasive blast (DAB) cleaning. WAB cleaning may be specified when dust suppression is desired, and may also be a means for reducing soluble salt contamination. The WAB cleanliness level specified should be the same as the corresponding degree of cleaning specified if DAB cleaning were the process being used.

The focus of this standard is Near-White Metal WAB cleaning. The five degrees of WAB cleaning are as follows:

Near-White Metal WAB cleaning provides a greater degree of cleaning than Commercial WAB cleaning (SSPC-SP 6 [WAB]/NACE WAB-3) but less than White Metal WAB cleaning (SSPC- SP 5 [WAB]/ NACE WAB-1).

Near-White Metal WAB cleaning is used when the objective is to remove all rust and other corrosion products, coating, and mill scale, but when the extra effort required to remove all stains of these materials is determined to be unwarranted.

Near-White Metal WAB cleaning allows staining on no more than 5% of each unit area of surface, while commercial WAB cleaning allows staining on no more than 33% of each unit area of surface. White Metal WAB cleaning does not permit any staining to remain on the surface.

This standard references the three levels of flash rust as defined in the SSPC/NACE joint standards for waterjetting (see Paragraph 3.1 in this standard).^5-8 Additional information regarding flash rust is provided in nonmandatory Appendixes A, B, and C.

Steel surfaces prepared by WAB cleaning can develop flash rust within minutes after the cleaning is completed. The project specification often contains requirements for the permissible level of flash rust before coating application. Additional information is provided in Paragraph A1 in Appendix A and in Appendix C.

This standard was prepared in 2015 by SSPC/NACE Joint Task Group (TG) 350A "Near-White Metal Surface Preparation by Wet Abrasive Blast Cleaning." TG 350A is administered by SSPC C.2 Surface Preparation Group Committee and NACE Specific Technology Group (STG) 04, "Coatings and Linings, Protective: Surface Preparation." This joint standard is issued by SSPC/NACE under the auspices of SSPC C.2 and NACE STG 04. This standard is one of a set of five standards on the degrees of surface cleanliness to be achieved by WAB cleaning.

In SSPC/NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the SSPC/NACE Joint Publications Style Manual, Paragraph 2.2.1.8. Shall and must are used to state mandatory requirements. The term should is used to state something considered good and is recommended but is not mandatory. The term may is used to state something considered optional.