Theory of hot galvanization:
The hot galvanizing process is a process in which parts produced after immersion in a melt are covered with pure iron or iron alloys that bond with metallurgical (metallic) bonds to the base metal (iron).
At present, this process is done in both galvanized and dry form.
In the galvanized, a mixture of zinc ammonium chloride is sprayed on the melt surface, and the melt is introduced into the melt immediately after the process of preparing it directly into the flux.
In dry galvanized parts, the parts are placed in a solution of ammonium chloride on the surface after being prepared in the drying agent and further into the melt.
The history of galvanizing is back to 1724. When a French chemist Melouin at the Royal Academy of France described a coating method on the iron on the melt.
In 1836, another French chemist, Sorel, continued. He first cleaned nine times in sulfuric acid to cover iron by zinc and then immersed it with flux of ammonium chloride and placed in a reservoir on the molten to form the first galvanized steel part.
Hot galvanizing is always a matter for the craftsmen due to increasing the life span of the components in terms of increasing their resistance to chemical and electrochemical corrosion in most industries, especially in areas exposed to corrosion.
Other galvanizing methods include:
Zinc plating (electrochemistry)
Mechanical spraying on the Sheradizing (zinc powder in the drain)
Spray on Zinc spray (circular spray method by burning heat)
Zinc rich paint coatings
Degreasing Fat
• A hot bath of a profit (about 90 degrees centigrade) or special fatty acids usually used in the first galvanized process station to remove the surface of the components from paint, oil, grease, and any other components.
• Other compounds that contaminate the surface and are not removed at this stage are removed in the next step (acidification).
• All discarded surfaces of the paint must be carefully monitored; some types of colors may not be easily removed; therefore, they require special mechanical operations such as sand blasting.
• The parts that are supposed to be galvanized need to be kept in place during the process.
Loading - jigging Loading - Suspension
For this purpose, a gun must be provided to allow the parts to be suspended during the preparation and immersion stages.
• This note reminds Rhonda that any contaminants such as paint, grease, oil, etc. should be removed from the surface before the start of the preparation.
• The positioning and internal porosity of the components must be such that the washing and melt solutions can be applied to all parts of the unit.
• Components of structures at design should be predicted in such a way that the area is not deadlocked, so that air, washing solutions (fatty acids, acids and fluxes) and, finally, the melt are not accessible.
• Be sure to coordinate at the beginning and during the process of designing and constructing galvanizing structures.
• Acid acid pickling
• The parts are then immersed in a bath of chloride in order to remove rust, shell and other metal oxides.
• The surface of the steel should be completely removed from these impurities, so that the melt can be fully reacted to steel.
• Deep and heavy rust may not be easily removed by acid removal, therefore, it may be necessary to use other mechanical methods to clean the surface before acidification.
• Pre-fluxing of fluxing
• After acidifying parts, they are immersed in a bathtub and at the end of the preparation process they are placed in a warm bath of ammonia chloride on and placed on it.
• A solution of ammonium chloride on the surface of steel for molten reaction.
• Hot dip galvanizing hot galvanizing
• The melt is reacted with a steel surface completely discontinued in the previous steps, and it forms a layer of zinc-iron alloys, which has a very strong bond with the steel surface.
• Galvanized coating is formed in the first 2 to 3 minutes of entering the melting bath, which in any case depends on the thickness of the steel.
• Quenching the cooled
• Upon completion of the hot galvanizing process, which is accompanied by the removal of parts from the melt, they immerse them immediately in water or in a solution of sodium dichromate.
• Dipping operations in sodium dichromate solution cause cooling of the parts, which is why it can be easily transferred and the surfaces will be deactivated and shiny as a result of subsequent reactions.
Characteristics Features
• Alloy coating on zinc may contain 80% to 100% coverage.
• Iron alloys are 250 times harder than steel
Coating comparisons. Cover comparison
• Hot dip galvanizing (HDG) galvanized coatings are preferred in comparison with zinc electroplating (ZEP) and continuous galvanizing (GC)), because
• Galvanized enamel coating, resulting in a lifespan of over 50 years without rust.
• Hard galvanized coating is harder and 5 times more wear resistance than other methods.
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