Feature: The key to smooth epoxy coatings

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Smooth and efficient spraying of epoxies requires special sprayers.
When properly catalyzed and applied, epoxies produce a hard finish that provides high resistance to water, alkalis and acids. Typical end uses include concrete and steel structures. However, they have certain characteristics that set them apart from other materials to be sprayed, and which influence the type of sprayer used.
The majority of epoxies are extremely abrasive, so need to be sprayed with equipment that is specifically designed to cope with their high abrasiveness. At the very least this means a robust pump incorporating hard, durable materials such as carbon steel, tungsten carbide and specific coatings. At the same time however, epoxies are not corrosive, so you don’t need to specify stainless steel or other anti-corrosive materials.
Not only are epoxies abrasive, they are difficult to manage. One reason for this is that they are heavy. In this respect, don’t confuse weight with volume! Hardeners tend to have lower densities than resin components. So an epoxy mixing system with a 5:1 weight ratio can easily end up as a 3:1 system if the components are measured per volume; again, leading to unexpected problems.
And remember to look carefully at the product expiration dates. Epoxy products that are past or even approaching their shelf life expiration tend to have fillers that have sunk to the bottom of the pack. Unless thoroughly mixed, this could result in a patchy result.
Epoxy coatings consist of one or two components. When two components are mixed – prior to application – an epoxy resin is cross-linked with a hardener or co-reactant. Proper mixing of the two epoxy paint components is essential. As it requires significant power to mix the two components uniformly, an electric mixer is indispensable. Measuring accuracy is also vital; even an error of 5% can lead to significant problems.
Finally, in some cases epoxies are heated. If this is likely for your particular application, then you need to select heat-resistant packings, made from a material such as PTFE.
However, no matter how well you have mixed your epoxy coating, the end result can still be negatively affected by a poor choice of sprayer. Graco offers four sprayer models that have been specifically developed to spray a broad range of epoxy coatings.
King airless sprayer
This rugged airless sprayer is highly appreciated for its dependability and durability to handle the toughest protective coatings such as epoxies. It incorporates the MaxLife pump that’s designed for robustness and reliability in the most demanding jobs. Key features include the exclusive MaxLife sleeve rod, long-life ceramic balls (optional) for maximum versatility no matter what’s being sprayed, and a standard two-line outlet. A high intake/exhaust capacity in the air valve leads to a fast, smooth changeover, eliminating annoying minor blemishes in the finish.
When spraying epoxies, packings play a critical role in optimising spray performance by sealing pressure and holding material inside the pump. The tighter the seal, the better the performance. King sprayers incorporate no fewer than seven throat packings.
Thermally isolated poppets on certain models are insulated from motor castings which can often drop below freezing temperatures. The design of the poppets and external pilot lines virtually eliminates pilot valve freezing that can result in an instant stop.
The King sprayer is designed for simple maintenance, with a removable valve cover and easy access to poppet valves. A factory installed accessory box contains common items that every applicator should have on the job site. It includes throat seal liquid, air filter element, tool for poppet and air valve, pump filter cap O-rings, pump filter element, spare tip and gun filter. The box also includes storage space for your Graco XTR Spray Gun.
The Graco King sprayer is available in a variety of models, some of which are ATEX certified, with several sizes of air motor and lowers. It’s ideal for single component epoxies but can also handle multi-component epoxies with no problem.
E-Xtreme electric airless sprayer
This electric-driven airless sprayer is specifically developed to provide a flexible alternative to conventional air-operated sprayers for protective coatings. Thanks to its electric drive, noise levels are low, and icing is eliminated. The E-Xtreme is highly energy efficient, with a low kWh per litre sprayed. Compared to air-driven airless units, E-Xtreme reduces energy consumption by up to 80%.
The unit’s software minimises pressure drop effects during change-over. This leads to a significantly smoother and more uniform spray pattern. It also reduces the pulsation transmitted to the painter, resulting in reduced operator fatigue.
Operator experience is also enhanced by the reduced noise levels of the electric motor. The E-Xtreme runs at 68 dBA; much lower than the OSHA hearing conservation threshold of 90 dBA. Operators can thus stay close to the unit for a longer time, which increases job productivity. A further advantage is that the pump stalls under pressure, preventing pump failures from clogged lines and reducing maintenance.
Rugged and reliable for both indoor and outdoor applications, E-Xtreme sprayers are ATEX and IECEx approved for use in hazardous locations or where generating a spark is a concern. They work on a standard residential 240 V, 16 A single-phase power supply. Powerful enough to spray most common medium to high solid materials, they provide sufficient volume for the most popular tip sizes. If you’re using a pneumatic sprayer and are thinking of replacing it with an equivalent electric sprayer, the E-Xtreme is ideal as it uses the same operational logic.
XP plural component sprayer
Engineered for projects that require faster-setting two-part coatings, Graco XP sprayers are easy to use and provide on-ratio, excellent spray quality for fast-curing materials. They provide the reliable performance necessary for challenging two-component projects. Their gravity feed design eliminates the need for feed pumps, reduces material waste and uses less clean-up solvent as only mix material is flushed.
XP sprayers provide an extremely consistent viscosity and therefore spray quality which makes them ideal for spraying large surface areas and producing an outstanding finish.
These mix-on-demand sprayers provide a high degree of flexibility for mix ratio, pressure and flow rate. Just choose the right system for the application. It’s easy to change the ratio by simply changing out one or two pump lowers. The XP sprayer is also available with a hydraulic motor; its low noise makes it ideal for indoor applications. With the XP, mixing at the gun is possible, which reduces both material waste and use of cleaning solvent.
XM plural component sprayer
Graco XM sprayers are designed to spray the toughest plural component materials, with the assurance that you’re spraying accurately and on-ratio. Each Graco XM is fully configurable – simply start with a base unit and select additional components required for your application. Featuring advanced features such as ratio accuracy control, ratio assurance, and data download, the XM range is ideally suited to meet the most demanding variable, high-volume epoxy coating jobs.
With the XM, material mixing reaches a new level of precision due to new dosing technology. The minor component (or side B material) is injected at high pressure into the major material (side A). Advanced sensors allow pumps to compensate for pressure fluctuations, resulting in accurate, on-ratio mixing for better yield and less waste. Ratio control can be user adjusted from 1:1 to 10:1.
Another key feature is that the linear sensor is integrated in the motor. This keeps dirt out and prevents the sensor being affected by heat. The fluid path of both the XP and XM is free of obstructions such as flow meters, integrators etc. which avoids clogging and reduces maintenance.
Like the XP, the XM is also suitable for high volume applications, such as a large boat where you need to spray with two or three guns, which is easily possible with the XM.
With both the XM and XP, short pot life of epoxies can be easily managed, compared to the King or E-Xtreme sprayers, because they mix on-demand, which also increases productivity. Epoxies can also be applied at high ambient temperatures with the XM and XP sprayers; very useful for applications in the Middle East or other hot environments where the heat will further shorten pot life.
Let’s look at three companies that are using some of these Graco sprayers for epoxy coatings.
Steel pipe coating plant, Turkey
Located near Antakya, Turkey, this particular company manufactures and coats spiral welded steel pipes of diameters between 170 and 3540 mm and wall thicknesses between 3 and 25 mm. End uses include pipes for drinking water, irrigation water and boreholes.
The company was looking for a 2K sprayer to apply solvent-free epoxy onto the internal surface of their spiral welded steel pipes. Previously they were using 1K airless sprayers but were considering moving to 2K airless sprayers to reduce costs, shorten spraying time and increase productivity.
Via Graco distributor Fresko, the company heard about the Graco XM70 2K sprayer and was interested in its potential advantages. Negotiations proceeded smoothly, and a unit was installed without a production stop being necessary. Operators quickly learned how to use the XM70, which was put into service with Graco Monark 5:1 feeding pumps and agitators for 200 litre drums. The epoxy coating used was AkzoNobel International’s Interline 975 or equivalent.
After even a short period of operation, the XM70 proved its value. It reduced the waste of materials and solvents, allowed a highly precise mix ratio of materials, and reduced the time necessary for mixing and spraying.
Metal construction company
in Greece
Established in 1994 by Pericles Navrozoglou, Elmet is one of the largest metal construction companies in north-west Greece. The company uses state-of-the-art machinery to produce iron works, aluminium frames and metal frames for stadiums, poultry and dairy farms, gas stations, and warehouses.
Elmet was already using spray machines to coat metal frames with epoxy and fireproofing coatings, both on their own premises and on site. As they work with so many different sorts of paint, depending on the demands of each job, they were looking for an efficient sprayer capable of handling a broad range of materials.
The company contacted Graco distributor Kolleris Bros Co. to find the best solution to combine energy efficiency and performance. Although air supply was not an issue, Elmet needed a sprayer which would not force them to transfer massive loads of air from outside the factory.
After discussions, calculations and precision planning, Elmet chose the Graco e-Extreme EX45. Although Elmet owns large compressors, the benefits of the e-Xtreme EX45 such as mobility, smooth operation, better spray results, along with reduced energy consumption, played a major role in them selecting it as their primary coating unit.
E-Xtreme’s effectiveness has been proven, since Elmet has sprayed tons of coatings successfully. However, the true success for Elmet was achieved with fireproofing applications. Strict safety regulations require most of their metal frames to be coated with fireproof paints. Elmet’s experienced staff managed to produce a fine coating solution by using 0.021” and 0.023” XHD tips, and appreciated the smoothness, low noise and quality finish of the pump.
Russian construction company
With more than half a century of experience, Yuzh Tekhmontage is one of the oldest companies specialising in construction in the south of Russia and has over 2,000 employees. Their major activities include initial construction, reconstruction and repair of oil refining facilities, and industrial production of construction materials. They mostly work on steel manufacturing projects.
Due to pressure limitations, Yuzh Tekhmontage’s electric driven sprayers were no longer effective. Therefore they started looking for a new airless sprayer with an electric power source to spray high-volume solids epoxy coatings.
Local Graco distributor Premium Class proposed to run a test with Graco’s e-Xtreme EX45 to apply the two-component epoxy coating. The EX45 is a portable unit (mounted on a cart) that sprays with a pressure of 310 bar, so has the performance capabilities to comply with all necessary requirements for this project. Hempel Hempadur Multi-Strength 45751 material was applied on a steel construction without any issues. The operator specifically noted the convenience of spraying without pulsation.
After this successful demonstration, Yuzh Tekhmontage chose the e-Xtreme for their plant. One of the key reasons for their decision is the possibility to spray high-volume solid materials. Its reduced pulsation and smooth, effective operation were also important factors. Moreover, the simple maintenance of the unit and its 240V/16A electric power cord were additional benefits.
The e-Xtreme unit handled the material easily without adding 10% of thinner. “We especially liked the higher pressure and easy maintenance, compared to the sprayer we had before,” says Evgeniy Kabalaliev, Chief of Production Areas at Yuzh Tekhmontage. “An extra benefit for the operator was the possibility to reach the desired wet film thickness with one or two passes instead of the three that were previously necessary. To choose the right tip size, we used the one suggested by the material manufacturer that’s also in the product’s technical data sheet. Also, we carefully checked the material pot life time after mixing the two components.”

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