Preparation of steel substrates before application of paints and related products-Visual assessment of surface cleanliness - Part 2: Preparation grades of praviously coated steel subs
1 Scope
This part of GB/T 8923 specifies a series of preparation grades for steel surfaces after localized removal of previous paint coatings. The various preparation grades are defined by written description (see clause 4) together with the representative photographic examples given in ISO 8501-1. In addition, photographs showing examples of preparation grades P Sa 2 and P Ma are given.
This part of GB/T 8923 is applicable to surfaces prepared for painting by methods such as blast-cleaning, hand-and power-tool cleaning, and machine abrading.
This part of GB/T 8923 relates the cleanliness of a surface to its visual appearance. In many instances this is sufficient, but for coatings like to be exposed to severe environments, such as water immersion and continuous condensation conditions, consideration should be given to testing for soluble salts and other invisible contaminants on the visually clean surface by the physical and chemical methods which form the subjects of the various parts of ISO 8502. The roughness characteristics of the surface should also be considered by reference to ISO 8503.
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.
GB/T 5210-2006 Paints and Varnishes-Pull-Off test for Adhesion (ISO 4624:20021), IDT)
ISO 2409:19922) Paints and varnishes-Cross-cut test.
ISO 4627:1981 Paints and varnishes-Evaluation of the compatibility of a product with a surface to be painted-Methods of test.
ISO 4628-1:19823) Paints and Varnishes-Evaluation of Degradation of Paint Coatings-Designation of Intensity, Quantity and Size of Common Types of Defect-Part 1: General Principles and Rating Schemes.
ISO 4628-2:1982 Paints and Varnishes-Evaluation of Degradation of Paint Coatings-Designation of Intensity, Quantity and Size of Common Types of Defect-Part 2: Designation of Degree of Blistering.
ISO 4628-3:1982 Paints and Varnishes-Evaluation of Degradation of Paint Coatings-Designation of Intensity, Quantity and Size of common Types of Defect-Part 3: Designation of Degree of Rusting.
ISO 4628-4:1982 Paints and Varnishes-Evaluation of Degradation of Paint Coatings-Designation of Intensity, Quantity and Size of Common Types of Defect-Part 4: Designation of Degree of Cracking.
ISO 4628-5:1982 Paints and Varnishes-Evaluation of Degradation of Paint Coatings-Designation of Intensity, Quantity and Size of Common Types of Defect-Part 5: Designation of Degree of Flaking.
ISO 4628-6:1990 Paints and Varnishes-Evaluation of Degradation of Paint Coatings-Designation of Intensity, Quantity and Size of Common Types of Defect-Part 6: Rating of Degree of Chalking by Tape Method.
ISO 8501-1:19884) Preparation of Steel Substrates before Application of Paints and Related Products-Visual Assessment of Surface Cleanliness-Part 1: Rust Grades and Preparation Grades of Uncoated Steel Substrates and Steel Substrates after Overall Removal of Previous Coatings.
3 Condition of the Painted Surface to be Cleaned
The degrees of degradation which may be found on previously coated surfaces shall be assessed in accordance with ISO 4628, parts 1 to 6.
If possible, supplementary information about the previous coating, concerning the generic type, number of coats applied, manufacturer's name, corrosive contaminants, adhesion and film thickness, shall be given.
4 Preparation Grades
4.1 General
A number of preparation grades, indicating the method of surface preparation and the degree of cleaning, are specified. The preparation grades are defined (see 4.2, 4.3 and 4.4) by written descriptions of the surface appearance after the cleaning operation.
Each preparation grade is designated by the appropriate letters "Sa", "St" or "Ma" to indicate the type of cleaning method used. The letter P before Sa, St or Ma indicates only localized removal of previous paint coatings. The number following, if any, indicates the degree of cleaning from mill scale, rust and previous coatings.
It should be realized that the various methods of cleaning do not give comparable results. The degree of cleaning shall be compatible with the generic type of coating system to be used for recoating.
Reference is made in 4.2 and 4.3 to the photographs in ISO 8501-1 which are representative photographic examples of preparation grades.
Note 1: The term "foreign matter" used in 4.2, 4.3 and 4.4 includes water-soluble salts and residues from welding flux. These contaminants cannot be completely removed from the surface by dry blast-cleaning, hand- or power-tool cleaning or machine abrading; wet blast-cleaning can be used.
Note 2: Mill scale, rust or a paint coating is considered to be poorly adhering if it can be removed by lifting with a blunt putty knife.
Note 3: The photographic representations appended to this part of ISO 8501 show some typical examples of steel prior to and after localized cleaning.
4.2 Localized blast-cleaning of previously coated surfaces, P Sa
4.2.1 Overview
Surface preparation by localized blast-cleaning is designated by the letters "P Sa".
Prior to blast-cleaning, any heavy layers of rust shall be removed by chipping. Visible oil, grease and dirt shall also be removed.
After blast-cleaning, loose dust and debris shall be cleaned from the surface.
Note: For descriptions of surface preparation methods by blast-cleaning, including treatment prior to and after the blast-cleaning procedure, see ISO 8504-2.
Foreword I
1 Scope
2 Normative References
3 Condition of the Painted Surface to be Cleaned
4 Preparation Grades
5 Photographs
Appendix A (Informative) Bibliography
GB/T 8923.2-2008 引用如下标准：
*ISO 2409:19922) Paints and varnishes-Cross-cut test. *ISO 4627:1981 Paints and varnishes-Evaluation of the compatibility of a product with a surface to be painted-Methods of test. *ISO 4628-1:19823) Paints and Varnishes-Evaluation of Degradation of Paint Coatings-Designation of Intensity, Quantity and Size of Common Types of Defect-Part 1: General Principles and Rating Schemes. *ISO 4628-2:1982 Paints and Varnishes-Evaluation of Degradation of Paint Coatings-Designation of Intensity, Quantity and Size of Common Types of Defect-Part 2: Designation of Degree of Blistering. *ISO 4628-3:1982 Paints and Varnishes-Evaluation of Degradation of Paint Coatings-Designation of Intensity, Quantity and Size of common Types of Defect-Part 3: Designation of Degree of Rusting. *ISO 4628-4:1982 Paints and Varnishes-Evaluation of Degradation of Paint Coatings-Designation of Intensity, Quantity and Size of Common Types of Defect-Part 4: Designation of Degree of Cracking. *ISO 4628-5:1982 Paints and Varnishes-Evaluation of Degradation of Paint Coatings-Designation of Intensity, Quantity and Size of Common Types of Defect-Part 5: Designation of Degree of Flaking. *ISO 4628-6:1990 Paints and Varnishes-Evaluation of Degradation of Paint Coatings-Designation of Intensity, Quantity and Size of Common Types of Defect-Part 6: Rating of Degree of Chalking by Tape Method. *ISO 8501-1:19884) Preparation of Steel Substrates before Application of Paints and Related Products-Visual Assessment of Surface Cleanliness-Part 1: Rust Grades and Preparation Grades of Uncoated Steel Substrates and Steel Substrates after Overall Removal of Previous Coatings. *GB/T 5210-2006 色漆和清漆拉开法附着力试验
