Preparing Galvanised Metals for Paint
What is Galvanizing? â—? Galvanizing is a general term for the metallurgical process that applies a layer of zinc metal over a steel surface in order to prevent corrosion of the steel. â—? In the corrosion reaction, the zinc layer will sacrifice itself to protect the underlying steel substrate. â—? In this electrochemical reaction, the zinc performs as the anode and the steel becomes the cathode. As long as there is adequate zinc, the steel will be protected from corrosion.
www.galvanizers.co.in
WHY DO WE PAINT GALVANIZING? ● ● ●
To Replace Lost Corrosion Protection To Extend Galvanizing Life with a Duplex System To Improve Appearance
www.galvanizers.co.in
1. To Replace Lost Corrosion Protection ● While the corrosion rate of atmospherically stabilized zinc is relatively low, the thickness of the zinc layer will continue to be reduced with time. ● Both the original zinc thickness and the severity of the atmospheric exposure will affect the life of the galvanizing. ● As the zinc layer is reduced through corrosion, its ability to protect the underlying steel substrate is diminished and the galvanic protection afforded by the zinc is lost. ● At this point, the application of a polymer overcoating may be considered to extend the life of the structure. www.galvanizers.co.in
2. To Extend Galvanizing Life with a Duplex System ● There are situations where new HDG may be immediately overcoated to extend the life of the structure beyond the longevity afforded by the zinc layer alone. ● When new HDG is overcoated with an organic coating, a synergistic effect is created that extends the life of the galvanizing. The organic overcoating becomes a barrier to penetration by moisture that slows down the corrosion of the zinc layer. ● A duplex coating system can extend the life of a galvanized coating by a factor of from 1.4-to-2.7 times the sum of the lives predicted for each coating layer alone. www.galvanizers.co.in
3. To Improve Appearance â—? Because the natural appearance of metallic gray spangling may be objectionable, HDG is often overcoated with an organic coating to improve its appearance or impart a specific color required by an architectural rendering. â—? In these situations, the addition of an overcoat will extend the life of the galvanized layer.
www.galvanizers.co.in
Problems With Painting Galvanizing â—? Galvanizing can be a difficult surface for the successful retention of an organic paint film. â—? Difficulties arise when surface contamination is not recognized and removed before the galvanizing is coated. â—? There are many possible types of surface contamination on galvanizing that must be removed before painting is attempted.
www.galvanizers.co.in
Preparation of Galvanized Steel Before Painting There are four recognised methods of surface pretreatment that produce a sound substrate for paint coating.
● ● ● ●
T-Wash Etch Primers Sweep Blasting Weathering www.galvanizers.co.in
How To Paint Galvanized Metal 1. Wash the metal thoroughly with hot soapy water. 2. Rinse the metal and let it dry completely for several hours. 3. Rinse the metal with a weak solution of water and ammonia and allow it to dry. 4. Remove any handles or other attachments from the metal. 5. Sand the entire metal surface thoroughly, including crevices and dents. 6. Wipe the entire surface with the tack cloths. 7. Apply the primer as directed, covering the entire surface of the metal. It's best to start at the top and work down, section by section. Continue‌
www.galvanizers.co.in
8. Wipe off any drips that appear as soon as possible. 9. Let the primer dry according to the directions. 10. Inspect the surface carefully to make sure it's completely coated with primer. 11. Read the directions on the container of metal paint. 12. Apply the metal paint -- which should be the same brand as the primer -- according to the product directions. 13. Let the paint dry according to the directions.
www.galvanizers.co.in
• Tanya Galvanizers has very good experience of all the products including Hot Dip Galvanization.
• Tanya Galvanizers has built up their high
Why Tanya Galvanizers
performance to their each products through innovation and quality reputation.
• Hot Dip Galvanizing and Manufacturing activities is backed with a highly talented, strong and efficient team.
• Well organized and highly advanced infrastructure
www.galvanizers.co.in
Contact Us http://www.galvanizers.co.in/
https://www.facebook.com/galvanizers
https://twitter.com/galvanizerindia
+91 (0265) 2632517
www.galvanizers.co.in