Login Close. Communicate with the galvanizer Determine condition of the surface Clean the surface Profile the surface Bake Powder coat Cure the powder coating Communicate with the galvanizer.
Determine the condition of the surface. Newly Galvanized Newly galvanized steel has been exposed to the atmosphere for a short time, typically less than 48 hours, and has few zinc compounds on the surface. Partially Weathered Partially weathered galvanized surfaces are typically present from two days to one year after galvanizing, depending on temperature and humidity conditions.
Clean the surface After the surface condition of the galvanized piece has been identified, the part is ready to be cleaned. Alkaline Solution A mild alkaline solution, a mixture of ten parts water and one part alkaline cleaner, can remove all organics from the surface without damaging the galvanized coating. Acidic Solution. Solvent Cleaning Finally, solvent cleaning, applying solvents to the surface using a clean cloth, can be used.
Profile the surface Once cleaning is complete, it is necessary to profile the surface for good powder coating adhesion. Sweep Blasting. Zinc Phosphate Solution An alternative method of profiling is to passivate the surface with a zinc phosphate solution.
Grinding The final option for profiling the part for powder coating is to grind the surface with power tools such as grinders or sanders. Powder Coat. Cure the Powder Coating After the powder application, the part should be placed in the curing oven. Inspector Listing - Non-U. Galv KnowledgeBase Preparing the hot-dip galvanized steel surface for painting or powder coating Dr. Necessary Required. Cookies that the site cannot function properly without. This includes cookies for access to secure areas and CSRF security.
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At present, high-build epoxies are widely used although water-based products, including polyurethanes, are now being specified. They are less tolerant of poor pre-treatment but their use could continue to grow as the Solvent Emissions Directive becomes more stringen. Painting and powder coating.
Painting galvanized steel Read More. Now you should be able to powder coat without any defects. I think the time is more so the galvanized coat evaporated some gas dust to the zinc brightener which may make this problem so you must checked your powder supplier.
Hi everybody, We are setting up a new powder coating plant with the following; 1. What is the difference in Galvanized passivation and this passivation. Powder Coating : We want to powder coat Galvanized Steel, which is the best quality of Galvanized steel to be used, and why? I am a quality engineer with a UK tube manufacturer. Some of our customer's have recently encountered problems powder coating our tube. The tube in question is formed from low carbon pre-galvanized steel strip, it is then welded via high frequency induction welding and the excess weld is then removed.
This tube is sometimes rejected because of a poor finish after powder coating along the repaired area. My questions are: 1 Are the temperatures during the powder coating process affecting the weld repair adhesion? Hi Mark from a fellow Brummy, Although you do not state if the problem is confined to the weld mark area or a general overall problem but I will try to answer your 3 Q's. Yes to all three. Temperature has a great deal to do with adhesion. Failure to bake for the recommended time and temperature is one cause.
Porosity of the galv will cause defects such as pin-holing. A waterborne primer or etch primer wash primer will overcome all your problems, although I can not see how you would confine it's application to one particular area i. Coating the complete tube would be most beneficial. Hi, I work for a tube manufacturer as well and am having an extremely similar problem to the one described above. To add to this - we have found that if we allow the tubes to bypass the wash of the powdercoaters i.
If we wash it ourselves, and let it go through the wash, the defects are there. Other tube manufacturers do not have the problem at the same place, and to the best of our knowledge have a similar process.
Any ideas here? Thanks, -Jason. Hi, Please advise process for powder coating on MS sheet. Sorry, Amrish, the answer is "c". Proper cleaning, acid activation, and fluxing must precede galvanizing, but phosphatizing or equivalent pretreatment must precede powder coating as well. Good luck.
Hi, What pre treatment should we do before powder coating on Electro-Galvanised Steel? Should we need to do the 7 step pre-treatment as done in case of Powder Coating on Hot Dipped Galvanised Steel or there is some other process? What is "electro-galvanized"? Either its galvanized or electroplated.
Both zinc coatings require pretreatment, the same treatment. Adhesion to zinc surfaces is the issue, not how the zinc got there. Pretreatment - possible stages including either chromate or zinc phosphate. It's not a phrase that you or I like, Geoff, but it's out there. Zinc electroplating electrogalvanizing virtually always includes chromate conversion coating, Amrish. So if you powder coat it while it's still fresh, nothing should be required but mild cleaning. Is this method okay?
For this reason the maximum size of the steel fabrication to be powder coated will be limited, but powder coatings can be applied successfully to hot dip galvanized surfaces. The thermal characteristics of galvanized steel are almost identical to those of ungalvanized steel for powder coating purposes and there are many examples of steel which has been galvanized and then powder coated.
However, when powder coating metals, the pre-treatment of the galvanized surface will depend upon which of the many powder types such as polyester, epoxy, or hybrid is being used. This usually includes a form of chemical pre-treatment such as chromating or phosphating, gentle heat treatment, followed by application of the powder.
The successful application of a powder coating to any metallic surface requires the multi-step instructions provided by the powder manufacturer to be respected in every detail.
For this reason an experienced or approved applicator should be asked to do the work. For powder coating metals, just like with wet painting, a full range of colours is available.
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