Incomplete curing: Polyester powders are thermosetting resins that cross-link to their final organic form by being maintained at a temperature (typically 180 o C), for about 10 minutes. What are the problems with Powder Coating over Galvanizing? Other application methods also exist. Pre-heating of the heavier work will assist in accelerating the curing process in the curing oven. One of the most durable protective coatings for steel is provided by applying a polyester powder coating over hot dip galvanized steel to provide a high grade architectural finish to steel items. It is essential that hot dip galvanized items are not quenched * 2 after galvanizing. The three main problem areas associated with the powder coating of hot dip galvanized steel products are: Pin holing of the coating The powder coating industry in China is in urgent need of legislation. 1. Many specifiers mistakenly presume that all powder coat … Cleaning functions most importantly in maximizing powder coating results, Attending 124th CANTON FAIR from Oct 15-20, Four Basic Pieces of Equipment for Electrostatic Spray Systems, Methods of Applying Powder – ELECTROSTATIC SPRAYING, A summary of the key properties of each generic type of thermosetting powder coating, Typical examples of thermoplastic powder coatings, Repair of parts and hanger stripping in powder coating. * 2 Note : It is equally important that the unquenched hot dip galvanized surface is kept clean and dry prior to powder coating. The aluminum coating forms a difficult-to-remove oxide that interferes with bead wetting and generates arc instability with spatter. The Automated Conveyor Carrier System – ACC® – Game Changing Innovation from TTX, PCI Powder Coating Events 2021-Next: Webinar Jan 20-Automatic Spray Systems, How to Get Started With Powder Coating – The Basics, IHEA Combustion Training Videos + other Training Events, Workshops for Warriors-JOIN FORCES TO HELP VETERANS. A Performance Polymer Alloy Coating specifically designed to provide a long lasting tough coating for a wide variety of exterior applications to mild steel, galvanised steel and aluminium. Light shotblasting is not really an adequate pretreatment. Incomplete curing of the polyester resin. These bubbles form small craters on … The problems associated with powder coating over hot dip galvanizing have not changed and inquiries are regularly received from throughout Australia asking advice following the failure of powder coatings over hot dip galvanized products. There is some skill involved in applying powder coating, and sometimes, no matter how experienced or practiced we are, things can sometimes go wrong. Powder coating over galvanizing presents it’s own set of problems to the powder coater but nothing we can’t overcome easily with a little knowledge on how to do it correctly. Do not leave outside, Keep the surface clean. Adjust pre-heat and line speed to ensure full cure. Diesel fumes will contaminate surface, If surface contamination has occurred or is suspected, clean surface with proprietary solvent/detergent designed for pre-cleaning prior to powder coating. powder coated. The practice is commonly called “duplex coating”. * 2 Note : It is equally important that the unquenched hot dip galvanized surface is kept clean and dry prior to powder coating. For any application, powder coating offers distinct advantages over galvanizing. Polyester powder coating over hot dip galvanized steel provides a high grade architectural finish to steel items with excellent atmospheric weathering characteristics.The powder coated product ensures maximum durability for steel components, which will generally provide 50 year+ rust free life spans in most architectural applications. Powder Coating Application Issues, Problems & Fixes. Being unfamiliar with industry standards. This ensures that the zinc surface is in a highly reactive state to accept the pretreatment applied in the powder coating process. How Can You Shave up to 30% off Shipping Materials & Improve Protection? This process can be difficult to perform properly if quality control procedures are not in place, and can result in uneven coating and … The three leading issues associated with the powder coating of hot-dip galvanized steel products are discussed below. Poor adhesion Surface treatment, … The goal is to remove any dust, dirt, or other particulate buildup that could affect … Control Your Powder Coating Process from Your Mobile Device-The Gema E-App, The Guide To Custom Matched Touch Up Paint, Powder Coating Remover – D-Zolve™319 Works at Room Temperature, How to Avoid Orange Peel Effect When Powder Coating, PCI Powder Coating Certification – Custom Coaters & OEMs Get Officially Certified, Mighty Hook Has a Hanging Solution for Everything Below the Conveyor. Use zinc phosphate pretreatment if highest adhesion is required. The three main problem areas associated with the powder coating of hot dip galvanized steel products are: Pin holing of the coating Poor adhesion Incomplete curing of the polyester resin Painting and powder coating Hot Dip Galvanizing by itself is a long lasting and cost effective means of corrosion protection. Hot-dip galvanized surfaces are not conducive to powder coating. This ensures that the zinc surface is in a highly reactive state to accept the pretreatment applied in the powder coating process. Black Spots Any damage or defects to the galvanised steel should be removed or rectified before the powder coating is applied, which should be done within 12 hours of galvanisation for best results. Pin-Holing If wet with rain or dew, it will rapidly oxidise and again cause coating adhesion and quality problems. ... 11 July 2017 . If a metal or material can’t hold an electrostatic charge, the powder won’t be able to affix itself to the surface, and it won’t be able to be powder coated. FEIHONG assist its partners to get through the epidemic situation. preparing and coating galva-nized structures. Pinholing: Pinholing is caused by the formation of small gas bubbles in the polyester coating during the stoving/curing cycle. Because this coating is not volatile like zinc-bearing coatings, weld soundness is not as much of a problem. There are four main problem areas that are common with powder coating on galvanised steel. Incomplete curing of the polyester resin. Thin, cold-rolled items having a very smooth surface finish and made from reactive steel may also cause coating delamination. Industrial Galvanizers commenced research in this area in 1986 which culminated in the construction of a purpose built powder coating plant at its Hexham (NSW) site in 1988 in conjunction with its galvanizing operations there. As with castings, the zinc application processes produce gases that can be trapped withinthesubsequentsurfacecoa~ ing. Posted by: FEIHONG Powders |on June 6, 2012. 3. All surfaces must be clean and free from grease. In the present work, polyester-based two coating systems have been investigated and t… What is the application of calcium carbonate in paints? The surface must be thoroughly cleaned and dry before the coating is applied. Iron phosphate has a slight detergent action and will remove small amounts of surface contamination. My customers need more resistant coating than standard specified (ASTM A123 [affil. In general, steel is protected from corrosive environments by conversion coatings, that is, phosphating, chromating, and so forth, and then followed by different layers of paints. Hot dip galvanizing is coating of metallic zinc bonded with steel to form a source of corrosion protection for steel. © 2021 PowderCoatingOnline.com. overpass on the Wallsend-Sandgate expressway link, hot dip galvanized and polyester powder coated in 1989 still in excellent condition in 1997. Even so there are still some problems during this application. These bubbles form small craters on the surface and are unsightly. Both coatings; however, are quite different in how they protect components and how they are manufactured. We select with high precaution our steel to … After the pretreatment, we could never see any signs of chromate on the GMS sheet, unlike the golden color on chromated aluminum sheets. Particularly for powder coatings, if the galvanized surface is not dry and powder is applied on top, the moisture will react with the zinc to form zinc oxide. ASTM International5 (ASTM)address-es the use of coating to repair new galvanizing in ASTM A 780, Standard Practice for Repair of Damaged and Uncoated Areas of Hot-Dip Galvanized Coatings, and ASTM D 6386, Standard PracticeforPreparationofZinc (Hot-Dip Galvanized) Coated Iron and Steel Product and However, ASTM D7803 includes a pre-heating step to drive off air and moisture from the prepared galvanized surface prior to powder coating. The three main problem areas associated with the powder coating of hot dip galvanized steel products are: Industrial Galvanizers investigations into these problems, in conjunction with major polyester powder coating powder suppliers, resulted in the cause of these problems being better understood, and polyester chemistry and plant procedures and design to be modified to allow a consistent, quality assured polyester powder coated hot dip galvanized product to be supplied. Without a competent pretreatment, powdercoating on galvanized steel will almost certainly lose adhesion. However, there are examples of early failures of duplex coatings due to incorrect specifications and poor practice. All Rights Reserved. Clean the surface. Powder coating galvanized steel for architectural applications is covered at present by EN 13438. Surface must be perfectly clean. This process cools the work so that it can be handled and passivates the surface of the galvanized coating to prevent early oxidation of the surface. We are having a big problem with powder coating on galvanized steel sheets. If wet with rain or dew, it will rapidly oxidise and again cause coating adhesion … Powder Coating Common Finishing Flaws & Simple Fixes – Echo Supply, Phosphate-Free Metal Pretreatment: ZIRCONIUM Pretreatment Systems. Many architectural projects done with this process in 1988 remain in excellent conditions today. Hot dip galvanized surfaces have been acknowledged as difficult to powder coat since the technology was first developed in the 1960’s. Use iron phosphate if standard performance is required. What are the Problems with Powder Coating over Galvanizing? Unlike powder coating, zinc coatings are available in only one color — silver — which can create severe limitations if you want to add visual appeal to your items. link to spec at Techstreet]). Powder coatings have demonstrated their ability as alternative to traditional solvent-borne coatings. 2020 New Year Holiday is from Jan 17 to Feb 1, Visit us in ChinaCoat Nov 18- 20 Shanghai, Attend 126th Canton Fair Oct 15-19,2019 – Powder Coating, Powder Coating Surface preparation – CLEANING ALUMINUM, FEIHONG Powders Attend 125th Canton Fair April 15-19,2019, Chemical surface preparation before powder coating. Chipping, fading and corrosion are common concerns when deliberating over the use of galvanized steel coating or powder coating for outdoor furnishings, such as handrails and guardrails, bike racks, playground equipment and park benches. https://www.chinapowdercoating.com/powder-coating-galvanized-steel The galvanized coating protects the base steel, supplying cathodic and barrier protection. Industrial Galvanizers commenced research in this area in 1986 which culminated in the construction of a purpose built powder coating plant at its Hexham (NSW) site in 1988 in conjunction with its galvanizing operations there. Very heavy galvanized coatings (more than 250 µm in thickness) may be fragile and delaminate from the surface upon impact and need more cautious handling in transport and erection. Techniques for Stripping Cured Powder Coating, How JAS Powder Coating Used WOW SHIPPING PADS To Boost Their Business – A Case Study, Powder Coating Transfer Efficiency – in detail, Get the PowerBoost® of 110,000 V / 110µA with Gema’s OptiFlex® Pro. Pre-heating the work in a pre-heat oven prior to powder application allows heavier hot dip galvanized sections to be powdercoated and deal with the problem of pin holing when used in conjunction with ‘degassing’ grades of polyester powder. Galvanized (zinc-coated)sub­ strates. Zinc phosphate has no detergent action and will not remove oil or soil. The main reason for pin holing appears to be that the discrete polyester resin particles in contact with the galvanized steel surface do not fuse at the same time as those on the surface of the polyester powder film, because of the mass of the galvanized steel * 1 , and the time taken for it to come up to fusion temperature. It could be that the lubricant applied to the galvannealed steel is too difficult to remove in a simple 60-sec spray wash. Zinc-coated steels are generally coated with a corrosion inhibitor that is meant to prevent the development of “white rust” or zinc … I am a steel fabricator and I have a problem with a lot of galvanised steel bars and plates (from 3/4" to 1" thick). Even though this standard is specific to powder coating of galvanized steel it contains the same cleaning and preparation techniques for the surfaces coated with liquid products as ASTM D6386 and SSPC-SP 16. * 1 Note : Hot dip galvanized items tend to be of heavier section thickness than other steel items, typically sheet steel, that are powder coated. We all know applying powder coatings can sometimes be tricky. One of the first ‘heavy’ powder coating projects undertaken in Australia – pedestrian bridge rail on the Janet Street Powder Coating Week 2021 – New Dates: April 27-30 – Register Today! Check for correct curing by solvent testing. The second step in producing powder coated galvanized steel is the application of the powder coat to the galvanized part. Best used for pre-galvanized products, Pre-heat work prior to powder application, Use ‘degassing’ grade polyester powder only. When organic coatings such as paint or powder coatings are applied over galvanized steel, the resulting combination is known as a duplex coating. Outgassing can occur when Ii powder coating is applied to a zinc-coatedsubstrate, galvanized steel, for example. It is essential that hot dip galvanized items are not quenched * 2 after galvanizing. Industrial Galvanizers of Australia investigates these problems, in conjunction with major polyester powder suppliers, resulting in the cause of these problems being better understood and polyester powder chemistry and plant procedures and design being modified to allow a consistent, quality assured polyester powder coated hot dip galvanized product to be supplied. Do not get surfaces wet. Powder Coaters Corner | How to Powder Coat, Powder Coating Equipment Replacement Parts, Hot dip galvanize and do not water or chromate quench, Remove all drainage spikes and surface defects, Powdercoat within 12 hours of galvanizing. An even layer of polyester powder coating is applied to the recently galvanized steel and cured in a stove at 180° C. Powder coatings must be applied within 12 hours of the galvanizing process. They also produce holidays in the coating that reduce its long term durability, particularly in aggressive (marine) environments. Like galvanized material, short-circuiting transfer with C-25 is the most commonly used welding method. Powder coating, while taking longer to apply, has more flexibility in finish and color. Warm to Touch has been developed to comply with UK Building Regulations which state that handrails need to be ‘slip-resistant and not cold to the touch.’ Advantages of Powder Coating 2. The painting of hot dip galvanized steel is an orthodox and well-proven practice in outdoor environments, both in Australia (AS/NZS 2312.2) and internationally (ISO 12944-5). The following specification is recommended: Properly applied powder coating over hot dip galvanizing will give exceptional performance. Do not transport uncovered loads. This particular coating of powder applied on the hot dip galvanizing process provides a significant amount of flexibility as well as a long life. The finished metal powder coating protects both the steel part and the galvanized layer, and provides an attractive exterior finish to the part. Systems, Supplies, and Equipment for Today's Powder Coaters. Poor adhesion: The final stage in the hot dip galvanizing process involves water quenching of the work, frequently in a weak sodium dichromate solution. Specially formulated resins with ‘degassing’ agents have been developed to alleviate this problem by delaying the onset of fusion of the powder. Much of the information in this article is based on the requirements of ASTM D6386, Preparation of Zinc (Hot-Dipped Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Painting and D7803 Preparation of Zinc (Hot-Dipped Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Painting for Powder Coating. There are a number of different abradable coating types, Production Profiling improves sales of powder coating products, Requirements for powder coating over hot dip galvanizing, The solutions for the problems of powder coating over hot dip galvanizing, The 127th Canton Fair will be held online from June 15 to 24,2020. The three main problem areas associated with the powder coating of hot dip galvanized steel products are: 1. The information on this website aims to avoid such failures by directing specifiers and applicators to the paint systems, surface preparation and application practices that will p… During the curing process of the powder coating, moisture trapped in the zinc oxide may expand and be released (called outgassing), causing pimples or blisters in the powder coating. This is a well-known fact because the technology was originally put together in the 1960s. Powder coating on hot dip, as can be understood from the name, is a procedure to apply a coating of a special powder on steel that is hot dip galvanized. These problem areas are likely to arise if preparation that was discussed previously is not completed efficiently. An even layer of polyester powder coating is applied to the recently galvanized steel and cured in a stove at 180° C. Powder coatings must be applied within 12 hours of the galvanizing process. Here are the four problem areas and the damage they can cause to your cladding: Building a Better Powder Coater Brand – Generate Leads! These items thus take longer to reach oven temperature because of their greater mass. In combination with hot dip galvanized coatings, the powder coated product ensures maximum durability for steel components, which will generally provide 50+ years rust free life spans in most architectural applications. A chemical conversion coating is better, using chromate, zinc phosphate or one of the newer silane based "dry in place" treatments. Pin holing of the coating Pinholing is caused by the formation of small gas bubbles in the polyester coating during the stoving/curing cycle. The presence of a passivating film on the surface of the galvanized coating will interfere with the zinc phosphate or iron phosphate pretreatment, and in many cases, render these pre-treatments ineffective. This technology produces very uniform coatings that have an attractive architectural finish with excellent atmospheric weathering characteristics. With hot dip galvanized items, with their heavier section thickness, it is necessary to ensure that sufficient stoving time is allowed to meet the curing specifications. Curing ovens are designed to provide this time at temperature combination. Nowadays, strict pollution laws and regulations are creating significant challenges for coating experts to develop an environmentally friendly product. Powder Coating vs. Galvanized Steel Finishes. Both provide protective finishes to metal components, but the powder coating is easier to scratch, dent, or crack under forceful impacts with sharp or jagged objects. Care must be taken in the powder coating process to avoid the formation of pinholes spots and uneven coating. When paint and galvanized steel are used together, the corrosion control provided is superior to either system used alone. Powder Coating vs Galvanizing Comparison The pretreatment line was originally used for aluminum pretreatment. A duplex system is simply painting or powder coating steel that has been hot-dip galvanized after fabrication. Hot dip galvanized surfaces have been acknowledged as difficult to powder coating since the technology was first developed in the 1960’s. Polyester powders are thermosetting resins that are applied electrostatically to the steel surfaceand cured at temperatures around 180 deg C (about 400 deg F). During the galvanizing process, gasses can become trapped within the surface coating. Additionally, a metal will need to be able to withstand the high temperature levels that are used during the curing process in order to be a good candidate for powdered painting. Posted in Powder Coating News | Tags: Polyester powder coating, Powder Coating Powder, powder coating pretreatment | No Comments ». 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