ASTM D7803-19
(Practice)Standard Practice for Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Powder Coating
Standard Practice for Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Powder Coating
SIGNIFICANCE AND USE
4.1 This practice describes the methods of preparation of hot-dip galvanized surfaces prior to the application of powder coating. The key to achieving proper adhesion between powder coatings and galvanized steel is surface preparation. The surface must be entirely free from visible metal oxides prior to powder coating. Any metal oxides that remain on the surface of the galvanized steel can potentially retain air or moisture. Upon heating during the curing stages of the powder application, the oxides may release water vapor or air, which can expand and penetrate the powder coating, causing blisters or voids.
4.2 The zinc coating is constantly in a state of change. From the time the steel part is removed from the galvanizing kettle, the exposed zinc coating interacts with the environment to form, first zinc oxides and zinc hydroxides, and then zinc carbonates.5 The process of complete conversion of the outer layer of zinc carbonates can take up to two years of exposure to the environment, depending on the local weather and moisture conditions.
4.3 The zinc surface after full weathering is very resistant to atmospheric corrosion because the tight patina that is formed (zinc oxide, zinc hydroxide and zinc carbonate) is dense and tenacious. However, during the formative stages of patina development, the oxide/hydroxide layer is poorly adhered and must be removed in order for the powder coating to adhere properly to the galvanized coating. The second is pinholing/blistering of the coating which can severely limit its potential performance, especially in aggressive chloride environments. Entrapped gasses developed during the galvanizing process escape the surface through the coating as it cures at high temperatures. If these volatile materials are not removed through an outgassing process prior to the baking of the powder, then pinholing or blistering can occur. The presence of pinholes gives chlorides and other corrosive agents access to the zinc substrate consequen...
SCOPE
1.1 This practice describes methods of preparing surfaces of hot-dip galvanized iron and steel for powder coating and the application of powder coating materials.
1.1.1 Powder coating is a dry finishing process which uses finely ground particles of pigment and resin, electrostatically charged, and sprayed onto a part to be coated. The parts are electrically grounded so that the charged particles projected at them adhere to the surface and are held there until melted and fused into a smooth coating in the curing oven.
1.1.2 Hot-dip galvanized iron or steel is produced by the immersion of fabricated or un-fabricated products in a bath of molten zinc, as specified in Specification A123/A123M or A153/A153M. This practice covers surface preparation and thermal pretreatment of iron and steel products and hardware which have not been painted or powder coated previously (Practice D6386). Galvanized surfaces may have been treated with protective coatings to prevent the occurrence of wet storage stain. This practice neither applies to sheet galvanized steel products nor to the coil coating or continuous roller coating processes.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7803 − 19
Standard Practice for
Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and
1
Steel Product and Hardware Surfaces for Powder Coating
This standard is issued under the fixed designation D7803; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
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1.1 Thispracticedescribesmethodsofpreparingsurfacesof 2.1 ASTM Standards:
hot-dip galvanized iron and steel for powder coating and the A123/A123M Specification for Zinc (Hot-Dip Galvanized)
application of powder coating materials. Coatings on Iron and Steel Products
1.1.1 Powder coating is a dry finishing process which uses A153/A153M Specification for Zinc Coating (Hot-Dip) on
finely ground particles of pigment and resin, electrostatically Iron and Steel Hardware
charged, and sprayed onto a part to be coated. The parts are A780 Practice for Repair of Damaged and Uncoated Areas
electrically grounded so that the charged particles projected at of Hot-Dip Galvanized Coatings
them adhere to the surface and are held there until melted and B201 Practice for Testing Chromate Coatings on Zinc and
fused into a smooth coating in the curing oven. Cadmium Surfaces
1.1.2 Hot-dip galvanized iron or steel is produced by the D4285 Test Method for Indicating Oil or Water in Com-
immersion of fabricated or un-fabricated products in a bath of pressed Air
molten zinc, as specified in Specification A123/A123M or D6386 Practice for Preparation of Zinc (Hot-Dip Galva-
A153/A153M. This practice covers surface preparation and nized) Coated Iron and Steel Product and Hardware
thermal pretreatment of iron and steel products and hardware Surfaces for Painting
which have not been painted or powder coated previously D7091 Practice for Nondestructive Measurement of Dry
(Practice D6386). Galvanized surfaces may have been treated Film Thickness of Nonmagnetic Coatings Applied to
with protective coatings to prevent the occurrence of wet Ferrous Metals and Nonmagnetic, Nonconductive Coat-
storage stain. This practice neither applies to sheet galvanized ings Applied to Non-Ferrous Metals
steel products nor to the coil coating or continuous roller E376 Practice for Measuring Coating Thickness by
coating processes. Magnetic-Field or Eddy Current (Electromagnetic) Test-
ing Methods
1.2 The values stated in SI units are to be regarded as the
F21 Test Method for Hydrophobic Surface Films by the
standard. The values given in parentheses are for information
Atomizer Test
only.
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2.2 Society for Protective Coatings Specifications:
1.3 This standard does not purport to address all of the
Surface Preparation Specification No. 1 Solvent Cleaning
safety concerns, if any, associated with its use. It is the
Surface Preparation Specification No. 2 Hand Tool Cleaning
responsibility of the user of this standard to establish appro-
Surface Preparation Specification No. 3 Power Tool Clean-
priate safety, health, and environmental practices and deter-
ing
mine the applicability of regulatory limitations prior to use.
Surface Preparation Specification No. WJ-1 Surface Prepa-
1.4 This international standard was developed in accor-
ration and Cleaning of Metals by Water-Jetting Prior to
dance with internationally recognized principles on standard-
Recoating
ization established in the Decision on Principles for the
Surface Preparation Specification No. WJ-2 Surface Prepa-
Development of International Standards, Guides and Recom-
ration and Cleaning of Metals by Water-Jetting Prior to
mendations issued by the World Trade Organization Technical
Recoating
Barriers to Trade (TBT) Committee.
1 2
This practice is under the jurisdiction of ASTM Committee D01 on Paint and For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Related Coatings, Materials, and Applications and is the direct responsibility of contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Subcommittee D01.46 on Industrial Protective Coatings. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Feb. 1, 2019. Published February 2019. Originally the ASTM website.
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approved in 2012. Last previous edition approved in 2018 as D7803 – 18. DOI: Available from Society for Protective Coatings (SSPC), 800 Trumbull Dr.,
10.1520/D7803-19. Pittsburgh, PA 15205, http://www.sspc.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7803 − 12 D7803 − 19
Standard Practice for
Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and
1
Steel Product and Hardware Surfaces for Powder Coating
This standard is issued under the fixed designation D7803; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice describes methods of preparing surfaces of hot-dip galvanized iron and steel for powder coating and the
application of powder coating materials.
1.1.1 Powder coating is a dry finishing process which uses finely ground particles of pigment and resin, electrostatically
charged, and sprayed onto a part to be coated. The parts are electrically grounded so that the charged particles projected at them
adhere to the surface and are held there until melted and fused into a smooth coating in the curing oven.
1.1.2 Hot-dip galvanized iron or steel is produced by the immersion of fabricated or un-fabricated products in a bath of molten
zinc, as specified in Specification A123/A123M or A153/A153M. This practice covers surface preparation and thermal
pretreatment of iron and steel products and hardware which have not been painted or powder coated previously (Practice D6386).
Galvanized surfaces may have been treated with protective coatings to prevent the occurrence of wet storage stain. This practice
neither applies to sheet galvanized steel products nor to the coil coating or continuous roller coating processes.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2
2.1 ASTM Standards:
A123/A123M Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products
A153/A153M Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware
A780 Practice for Repair of Damaged and Uncoated Areas of Hot-Dip Galvanized Coatings
B201 Practice for Testing Chromate Coatings on Zinc and Cadmium Surfaces
D4285 Test Method for Indicating Oil or Water in Compressed Air
D6386 Practice for Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Painting
D7091 Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied to Ferrous Metals
and Nonmagnetic, Nonconductive Coatings Applied to Non-Ferrous Metals
E376 Practice for Measuring Coating Thickness by Magnetic-Field or Eddy Current (Electromagnetic) Testing Methods
F21 Test Method for Hydrophobic Surface Films by the Atomizer Test
3
2.2 Society for Protective Coatings Specifications:
Surface Preparation Specification No. 1 Solvent Cleaning
Surface Preparation Specification No. 2 Hand Tool Cleaning
Surface Preparation Specification No. 3 Power Tool Cleaning
1
This practice is under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, Materials, and Applications and is the direct responsibility of
Subcommittee D01.46 on Industrial Protective Coatings.
Current edition approved June 1, 2012Feb. 1, 2019. Published June 2012February 2019. Originally approved in 2012. Last previous edition approved in 2018 as D7803
– 18. DOI: 10.1520/D7803-12.10.1520/D7803-19.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’sstandard’s Document Summary page on the ASTM website.
3
Available from Society for Protective Coatings (SSPC), 40 24th St., 6th Floor, 800 Trumbull Dr., Pittsburgh, PA 15222-4656,15205, http://www.sspc.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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