GB/T 8923.3-2009 Preparation of steel substrates before application of paints and related products - Visual assessment of surface cleanliness - Part 3: Preparation grades of welds edges and other areas with surface imperfections
Preparation of steel substrates before application of paints and related products - Visual assessment of surface cleanliness - Part 3: Preparation grades of welds edges and other areas with surface imperfections
This part of GB/T 8923 describes preparation grades of welds, edges and other areas, on steel surfaces with imperfections. Such imperfections can become visible before and/or after an abrasive blast-cleaning process.
The preparation grades given in this part are to make steel surfaces with imperfections, including welded and fabricated surfaces.
2 Normative References
The following normative documents contain provisions which, through reference in this part, constitute provisions of this part. For dated reference, subsequent amendments to, or revisions of, any of these publications do not apply. However, all parties coming to an agreement according to this part are encouraged to study whether the latest editions of these documents are applicable. For undated references, the latest edition of the normative document referred to applies.
ISO 12944-2 Paints and Varnishes-Corrosion Protection of Steel Structures by Protective Paint Systems-Part 2: Classification of Environments
ISO 12944-3 Paints and Varnishes-Corrosion Protection of Steel Structures by Protective Paint Systems -Part 3: Design Considerations
3 Types of Imperfection
This part of ISO 8501 deals with imperfections on:
——welds;
——edges;
——steel surfaces generally.
The various types of imperfection are illustrated and described in Table 1.
4 Preparation Grades
Three preparation grades for making steel surfaces with visible imperfections suitable for the application of paints and related products are as follows:
P1 Light preparation: no preparation or only minimum preparation needs to be carried out before application of paint;
P2 Thorough preparation: most imperfections are remedied;
P3 Very thorough preparation: surface is free of significant visible imperfections.
The significance of visible imperfections should preferably be agreed between all relevant parties, depending on the specific application.
Requirements for the preparation grades are given in Table 1.
Note 1 It is important that the preparation methods used to achieve these preparation grades are not deleterious to the integrity of the steel surface or welded areas. For example, strong grinding pressure can result in the formation of heat-affected areas on a steel surface, and removal of defects by grinding can leave sharp edges at the edges of the grind pattern.
Note 2 It is possible that different imperfections on a structure will require different preparation grades. For example, undercut (Table 1, 1.4) might require P3 preparation while all other imperfections might require P2 preparation. This can, in particular, be the case when there are requirements for the aesthetic appearance of the finish. In such cases, P3 could be specified even if there were no apparent corrosivity requirements (see ISO 12944-2).
Note 3 A replica, known as NACE standard RP 0178, showing examples of weld imperfections and certain levels of preparation, can be obtained from NACE International, PO Box 218340, Houston, Texas 77218-8340, USA.
