Are you interested in learning how to operate an aluminum coil coating line? If so, you’ve come to the right place. In this beginner’s guide, we’ll walk you through the basics of running an aluminum coil coating line, so you’ll have a better understanding of how to safely and effectively operate it. Let’s get started!
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Prepping the Aluminum
The first step in operating an aluminum coil coating line is to prepare the aluminum for coating. The main goal of this procedure is to create a surface that is free from dust, dirt, grease, and other contaminants so that the coating will properly adhere to the metal surface. This typically involves several processes, including cleaning, surface preparation, and pre-treating.
Cleaning
The most common cleaning processes for aluminum coil coating are degreasing and deoxidizing, which may require the use of specific cleaning agents and methods. For example, some popular choices include detergents, acids, and solvents, ensuring they don’t damage the aluminum surface.
Once the surface has been degreased and deoxidized, it is important to rinse the aluminum thoroughly with water to remove any residue that may be left behind. And, when it has been rinsed, it should be allowed to air dry or dried with a lint-free cloth to prevent any paint defects such as bubbles or drips.
Surface Preparation
Once the surface has been cleaned, you must further prepare it for coating. This can be done by sanding, brushing, or grinding, with the goal of creating a smooth surface that is free of defects such as scratches or dents. And, if there are any deep imperfections in the surface, you may need to fill them in with a special filler material.
Pre-Treatments
In some cases, a pre-treatment may be necessary to ensure that the coating adheres to the aluminum surface. Commonly, pre-treatments can include chemical treatments, etching, or powder coatings in order to create a stronger bond between the coating and the metal surface.
Applying the Primer
Applying the primer to the aluminum coil is an important step in the aluminum coil coating process since it will act as a base for the final coat of paint and provide added protection from corrosion and other damage. So, in order to ensure that your aluminum coil is properly prepared, you must carefully apply a thin layer of primer over the entire surface of the coil. And, once the surface is bone dry, and in case you think this is necessary, repeat the process until the desired number of coats of primer has been applied.
Applying the Paint
When it comes to applying the paint to your aluminum coil coating line, there are two methods for doing so: spraying and rolling.
Well, if you decide to spray, you will need to have a quality airless sprayer to ensure even coverage and minimize overspray. Also, make sure to use enough pressure and adjust the nozzle to the correct angle and distance from the material.
The other option is to roll the paint on the aluminum. This method works well when you have an even surface and are looking for a uniform finish. However, to roll on the paint, you will need a high-quality paint roller with a nap length that is suitable for the type of paint you’re using. And, once you’ve chosen a roller, apply the paint in thin, even coats, starting from one end of the aluminum and working towards the other end.
By and large, no matter which method you choose, be sure to apply multiple thin coats of paint until you reach the desired coverage level.
The Curing Process
Curing is the final step in the aluminum coil coating process that helps to ensure that the coating adheres to the aluminum and provides a long-lasting, durable finish. Overall, there are two main types of curing processes used for aluminum coil coatings: thermal curing and ultraviolet (UV) curing.
Thermal Curing
During thermal curing, the painted aluminum is exposed to high temperatures for an extended period of time, ensuring a strong bond between the coating and the metal forms. The most common temperature range for thermal curing is between 200 and 400 degrees Fahrenheit, and depending on the type of paint being used, the curing process can take anywhere from a few minutes to several hours.
UV Curing
In essence, UV curing is a quicker process than thermal curing, meaning the paint is exposed to ultraviolet light, which causes a chemical reaction that helps to cure the coating. This method is often used when quick turnaround times are needed. However, because UV curing does not provide as strong of a bond as thermal curing, it is typically only used for thin-film coatings.
And, regardless of which curing type you’ll utilize, it is important to monitor the curing process closely, as well as adhering to the manufacturer’s instructions for best results.
Bottom Line
With the right preparation and steps, operating an aluminum coil coating isn’t an impossible feat. Just be sure to clean the aluminum prior to coating, apply a primer and paint in the correct order, and finally, properly cure the end product. By taking these simple steps and following instructions as indicated, you are to confidently operate any aluminum coil coating line.
E-Coating (Electrostatic Coating) is a surface finishing technique that utilizes charged paint particles for coating metal parts. The paint electrostatically adheres to the surface through electrophoresis and results in a uniform thin film of paint. E-coating Aluminum is one of the popular surface finishings for aluminum parts.
It has been a widely adopted surface treatment method for aluminum parts due to its increased efficiency and economy. This guide will highlight the important aspects of e-coating to help you choose the right e-coating solution for your die cast or machined aluminum parts.
Sunrise Metal is a leading aluminum die casting and CNC machining manufacturer. We have multitudes of surface treatment facilities including e-coating. Need a supplier that can provide you with a one-stop solution for design, manufacturing, and finishing? Sunrise Metal wants to help.
E-coating is known by various other names in the industry such as electrocoating, electrophoretic deposition, electrophoretic painting, electrodeposition, etc. Regardless of the differences in names, they all refer to the same process.
The coating process takes place in multiple steps. The entire process of e-coating aluminum parts may be divided into the following steps.
Loading Parts
The treatment facility is equipped with a good number of immersion tanks. Usually, the manufacturers move the parts from one tank to another using conveyor belts. A human operator sorts the aluminum parts onto the e-coating line.
The parts must be hanged into the coating line in a manner so that it will not entrap any air when dipped into a tank. From there, the parts are carried into the pretreatment facility.
Pretreatment
In order to e coat paint an aluminum part, you must ensure that there are no impurities present in
the parts. Impurities can severely damage the surface of parts. It will also compromise the consistency and performance of the applied coating.
So, aluminum parts are thoroughly cleaned in a pretreatment facility first. A typical pretreatment facility consists of multiple chambers/tanks for rinsing the parts with demineralized water and other cleansing acid/chemicals.
Deposition
Once pretreatment is done, the conveyor belt carries the parts into a paint tank for deposition. Conveyor belts may not be suitable when dealing with large parts like automotive chassis. In such cases, another mechanism is used for handling the parts.
The paint pigment remains suspended in the liquid and electrostatically charged through an electric current of high voltage. The aluminum parts act like an electrode here and attract the charged paint particles.
The charged paint particles adhere to the part’s surface and form a thin film. The thickness of the coating can be regulated by modifying the voltage of the current. Higher Voltage will result in a thicker coating.
Rinsing
The dipped parts need to be rinsed again to remove the excess paint. They are carried into the cleaning chambers again, and thoroughly rinsed with water and chemical solutions. Once done, they are sent to the oven.
Curing
E coat paint needs to be cured in an oven for cross-linking the paint particles. This allows the paint to perfect its chemical composition and improve its properties. Curing substantially improves the adhesion of paint to the part’s surface and the paint won’t come off without aggressive means of removal.
Unloading Parts
After Curing is done the parts are allowed to cool down for a while and then they are unloaded from the e-coating line. Then a new batch of parts is loaded onto the e-coating line.
These processes can be performed manually as well. But when dealing with a large volume of parts, automation can substantially increase the efficiency of the process. Here’s a video that explains the e coating process in brief.
E-coating may be classified into the following categories based on the polarity used for coating.
Anodic E-coating
Cathodic E-coating
Anodic E-coating
In this case, the metal part is used as the anode. It is not a preferable e-coating technique and rarely used. Because it causes some metal ions to mix with the coating. This hampers the durability and corrosion resistance of the parts. However, anodic e-coating can be cured at lower temperatures.
Cathodic E-coating
The aluminum parts are negatively charged in case of the cathodic e-coating process. The part act as the cathode and attracts the negatively charged paint particles. This is the most common scenario for e-coating. It is more efficient and provides better results.
Cathodic e-coating can be done with different types of the coating material. Two such processes are,
Cathodic Acrylic E-coating
Cathodic Epoxy E-coating
Acrylic coatings provide good protection against UV rays and corrosion. It offers a wide range of colors, but the colors are a bit light.
Epoxy coatings provide superior protection against corrosion. But, they don’t provide good protection against UV light. So, they are mostly used as a primer in automobile parts and requires an additional coating over it.
E-coating is a popular surface finishing technique for aluminum parts. Its convenience and effectiveness are what make it a preferable option to others. Below we have highlighted the major benefits of e-coating aluminum.
Outstanding Durability
E coat paint is extremely durable. The paint adheres to the aluminum surface very well and will not come off under normal conditions. So, it will keep parts protected for an extended period thus eliminate the hassle of maintenance for end-users.
Excellent Protection
E-coating provides high resistance against corrosion for aluminum. So, the coating can withstand highly corrosive and harsh environmental conditions. It also increases the wear resistance of your aluminum parts.
Uniform Film Thickness
E-coating is very efficient and consistent. It offers a uniform film thickness all-around your aluminum parts. You can control the coating thickness by altering the voltage of the current supplied into the tank. So, you can choose a thickness according to your requirements.
Economical
E-coating is very economical compared to other similar coating techniques. It provides premium quality which would be significantly costlier to achieve using other methods. In fact, e-coating has substantially reduced the demand for many finishing methods that were once widely used in the industry.
Versatile
You can e coat almost any metal parts including aluminum. Part’s complexity is not an issue with e coating. Since the entire part is dipped into the tank, the paint can reach all recesses of the parts. And you can coat very large parts as well using larger immersion tanks.
For more coating aluminium coilinformation, please contact us. We will provide professional answers.
Environment Friendly
E-coating can utilize water-based solutions as the coating medium. There is little to no volatile organic compound present in the paint solution. So, unlike most other liquid coating processes, it doesn’t have a negative impact on the environment.
E-coating has many applications in the manufacturing industry. Some of the common application of e-coating aluminum is discussed below.
E-coating is extensively used in the automotive industry for coating automobile chassis and components. They are more or less a standard as primers for metal or aluminum components. Their superior adhesive properties allow you to apply an additional layer of coating with ease.
E-coating can also serve as a top-coat for your aluminum parts. They are desirable for their resistance to corrosion and wear. So, aluminum housing and frame components can benefit from e-coating. The performance and durability will be better than most liquid coatings.
E-coating is economical, efficient, and durable. It is a nearly perfect process that is excellent for coating your aluminum parts. But there are certain situations when e-coating may not be the best solution for you. Let’s have a look at some of the limitations of the e-coating process.
Limited Color Choice
E-coating is not actually limited to colors. It is possible to achieve a wide range of colors with e-coating. The paint solution can be consisting of different varieties of color pigments. However, it is not as simple as it sounds.
One immersion tank is usually used only for one type of color. If you want to e-coat of different colors then the entire paint tank needs to be refilled. This will take a considerable amount of time and cause a waste of material. So, you will find that the suppliers will offer you a limited number of colors for e coat paints.
Poor UV Ray Protection
Some e-coating materials such as epoxy has poor UV ray protection. This makes them prone to fail in outdoor conditions. However, this can be fixed by providing an extra layer of coating. Normally epoxy coated parts are powder coated afterward to improve their durability and performance.
Inconsistency in Color
It is difficult to control the color of e-coated parts in a batch. Because the outlook of the color can vary depending on the curing process. Parts with more oven time can look different from the ones with less oven time.
Defects During Coating
When you wish to e-coat your aluminum parts, they must not contain any form of impurities. Having even the slightest bit of impurity can cause severe e coat defects and compromise the part’s durability and performance. So, all parts need to be thoroughly inspected and cleaned.
Blind spots and sealed corners can entrap air inside the aluminum parts thus leave uncoated areas that would be prone to defects. This issue can be mitigated by immersing the parts in a suitable orientation.
People often confuse e-coating with other types of surface finishes due to their similar outlook. However, there are substantial differences between them in terms of performance and durability. Here we have discussed how e-coating differs from other similar finishing techniques.
E-Coating vs Powder Coating
Both the e-coating and powder coating process follows the same principle. The paint is electrostatically charged and deposited onto the part’s surface through electrodeposition. But e-coating is a wet process where the parts are immersed into a paint tank for coating. While powder coating is considered a dry process where the parts are sprayed with powder paint.
Powder coating involves spraying powder paint towards an electrostatically charged aluminum part. The paint particles are attached to the part’s surface by the electrostatic attraction. Upon curing, the solid particles melt and strongly adheres to the part surface.
Powder coating and e-coating have a lot of advantages in common and both are eco-friendly processes. However, powder coating is not as uniform as e-coating. And it is difficult to coat certain areas. So, the coating may lack consistency and uniformity when applied to complex parts.
It is often used as a secondary layer over an e-coated surface. Doing so can substantially increase the durability of aluminum parts. And you have access to more types of colors with powder coating.
E-coating vs Electroplating
E-coating or Electrocoating is an electrodeposition process where a metal part is coated using organic compounds like paint, epoxy, etc. Electroplating is an electrodeposition process are using metallic compounds to coat the part. Unlike, e-coating, the parts don’t have to be metal in this case.
Electroplating is typically done with nickel, gold, zinc, silver, etc. elements. The coating will provide a metallic sheen to the parts and enhance their conductive properties. Electroplated metals usually offer better hardness, and wear resistance for aluminum parts.
E-Coating Aluminum vs Anodization Aluminum
Anodizing does not actually involve applying an extra layer of coating on your parts. It is an electrochemical process that increases the natural oxide layer of metal parts to improve its appearance, performance, and corrosion resistance.
The appearance of an e-coated and anodized part of the same color may look similar. But their properties are entirely different. E-coating is applicable for almost any sort of metal. But Anodizing is mainly suitable to aluminum and few other metals.
Both of the processes can increase the corrosion and wear resistance of aluminum parts. The E-coated and anodized surface has excellent adhesion and suppliers often use them as a prime coat for other surface finishes.
We hope that this article was able to answer your queries regarding e-coating. If you are curious to know more about e-coating aluminum parts, you can contact Sunrise Metal for assistance.
If the product you want to powder coat has a lot of debris (rust, laser scale, preexisting paint), then you will likely need a Blast Room. A blast room is an enclosure where you use compressed air to propel abrasive material against the surface of your parts. Depending on the situation, you would typically use either an appropriate blast media (grit) or steel shot to blast all the unwanted debris off your part until it has a clean metal surface that’s ready for powder coating. Blast rooms are especially useful for job shops that work with raw materials that aren’t pristine, such as plate steel or tube stock that has areas of oxidation or welding residue. (For more information on getting the right blast room, go here.)
If oils, solvents or chemical residue covers any part of your products’ surface, you’ll want to consider a Wash Station. A wash station is where you spray your parts with a detergent and/or chemical pretreatment agent, such as iron phosphate. Using hot water or steam to clean and then chemically prep parts is quite common. A wash station helps you increase powder adhesion and improve finish quality, even if the parts have already been blasted. Some wash stations require you to apply the chemistry manually using a spray wand. Other washers are automated and the parts travel through the cleaning, rinsing and prep stages on a conveyor.
In some operations, pretreatment requires the use of a Dry-Off Oven. This is commonly an appliance similar to a curing oven, but where the just-washed parts are heated in order to evaporate any water or chemistry still on them. This step can also help parts reach an optimum temperature for powder application.
Pretreatment equipment is incredibly useful for your operation and can make a big difference in the quality of your work, but an elaborate system isn’t always required for powder coating. While we can’t stress how important it is to have a clean surface before you apply powder, expensive pretreatment equipment isn’t mandatory for entry level coating operations where hands-on cleaning (such as with a tack rag and solvent) can be employed as needed.
Powder coating application is almost always done with a special Powder Spray Gun. In order for powder coating to work effectively, the powder must be electrostatically charged. The only way to apply this charge is with a spray gun designed exclusively for powder coating. Compressed air moves powder through the gun from a hopper or directly from the box the powder is stored in. The compressed air blows powder out of the gun as a tightly formed cloud. As the powder leaves the gun, it receives an electrostatic charge. Once charged, the powder cloud envelopes the part and the powder sticks to the surface of the grounded part (which is one of the reasons why powder coating equipment is so easy for new operators to use).
If you want to powder coat, you need a powder coating gun. There are many types of powder spray guns available on the market. We always recommend investing in a professional-grade powder gun, as they are more reliable and provide better results.
Once you have your powder gun, you’ll need to have a place to use it. Whenever you spray powder, some of the powder will end up on the floor and in the air instead of on your products. This leftover powder is referred to as overspray. Keeping this overspray out of your workspace is one of the functions of the Powder Spray Booth.
The powder spray booth is designed to keep the rest of your shop clean while providing a well-lit area for you to apply powder coating. All powder spray booths will have one or more exhaust fans. The exhaust will use filters to capture at least some of the overspray. If the exhaust works properly and the filters are maintained, the airflow in the booth should keep the overspray inside the enclosure and enable the painter to see what he’s doing. If your shop environment includes welding or blasting areas, filtered doors on the spray booth can keep airborne contaminants out of your powder coated finish.
Numerous booth configurations are available, and getting the ideal booth depends largely on what you’re coating, your floor space availability, and your workflow requirements. Powder spray booths can be open-faced or have doors on one end. They can also be tunnel style enclosures with the filtration built into the floor or wall(s). If you have space constraints, a Powder Spray Wall may help you get the airflow and filtration you need. A spray wall is just a large filtration system—essentially a spray booth without walls or a roof.
If you want to recycle your powder, you need to make sure your powder spray booth is built with a reclamation system. Usually this system will rely on pleated cartridge filters. These help you recover some of the overspray and reuse it. This can be very cost-effective if you are planning to use only one color and type of powder for your coating. The spent powder is trapped in the filters and then dislodged into a recovery bin for reuse. In more advanced systems, the powder is automatically reconditioned, mixed with virgin powder, and then returned to the supply hopper feeding the powder gun(s). If you are planning to reclaim a variety of colors, a set of removable filter modules is required. Unfortunately, the cost of buying multiple reclaim modules can add up quickly because you can only reclaim one color in each filter module.
No matter what type of booth you decide on, you’ll need a powder spray booth if you want to get quality results and maintain reasonable throughput from your coating operation. (For more information on what size powder spray booth you might need, click here.)
If you have stringent finish requirements, you may also need a Clean Room (also called an Environmental Room). This is usually a climate-controlled room built around the powder application area. The purpose of a clean room is to eliminate airborne contaminants and control the temperature and humidity during powder application to prevent any sort of contamination, clumping or consistency issues when applying the powder. Clean rooms are often recommended if your shop environment is particularly dirty or your products require an exact specification for adhesion or salt spray tolerance. (For more about requirements, click here.)
After your product is powder coated, the final step is to place it inside a specially designed Powder Curing Oven. They usually operate between 325° and 450° Fahrenheit. Once the oven is up to temperature, the temperature stabilizes. The coated products are exposed to precisely heated air for a set period of time. Once the curing process is complete, the parts are removed and allowed to cool before being handled.
Some ovens use infrared emitters to heat the surface of the coated parts, but these types of electric powered or gas catalytic ovens can be costly to buy and expensive to maintain. More commonly, ovens rely on electric heating elements or a natural gas or LP-fueled heat system. These more conventional ovens typically rely on heated air moving over the parts for convection curing.
The time it takes to cure the powder varies greatly depending on the size, shape and thickness of the parts being coated. A small, light-gauge bracket can take as little as ten minutes to cure completely, while a 20’ section of heavy-walled pipe may take over an hour to cure properly.
If you want to powder coat at a professional level, the type of oven you choose is critical. Not only are brand-name powder curing ovens designed specifically to generate premium coating results, they are also highly efficient appliances in terms of fuel usage and energy costs. It’s likely that you’ll be using your oven several hours per week, so the cost of an inefficient design can quickly sap your profits.
Similar to powder spray booths, powder curing ovens come in multiple sizes and configurations. (For more information on what size powder coating oven you will need, click here.)
There are two basic configurations for any powder coating line: batch or automated.
A Batch Powder Coating Line is usually a system where the parts are prepared, coated and cured in batches of multiple parts, with operators handling up to dozens or hundreds of parts at a time. The products are usually hung on metal rolling racks, which move with the parts throughout the coating process. (Remember: high-temperature or metal casters for your racks are very important!) With a batch line, parts are usually moved from stage to stage manually, and the term “batch coating system” is also commonly used to describe operations where large objects are coated individually after being moved by hand or with machine.
An Automated Powder Coating Line uses basically the same appliances as a batch system, but connects many or all of the stages via a motorized conveyor that moves the parts through at a constant rate. The products are usually loaded onto the conveyor at a set location and move through each stage, where either manual operators or automated devices clean and prep the parts and apply powder to them. Once coated, the parts move through the curing oven and then cool as they travel along the conveyor to a point where they can be unloaded.
(For more information on whether a batch coating line or an automated coating line is right for your business, follow this link to learn more about the advantages and disadvantages of each system.)
Hopefully this Beginner’s Guide to Powder Coating Equipment has answered your basic questions about what powder coating is, how it is done, and what you need to start your first powder coating line. If you would like to learn more, please give us a call at (888) 770-0021. Reliant Finishing Systems’ specialists can help! We’ll guide you through the process of setting up a powder coating shop or adding coating capabilities to your existing fab shop or manufacturing facility. Whether it’s your very first powder coating system or you’re upgrading to a complete automated line, you can trust Reliant to provide you with sound advice and affordable, high quality equipment.
Updated Content Dec 9, 2020
The coil coating process (see Diagram 1) provides a way to rapidly apply a variety of paints in a uniform, controlled, continuous and quality fashion at line speeds varying from 100 to 700 feet per minute with the paint being cured in 15-45 seconds to achieve a Peak Metal Temperature of 390 to 480°F depending on the paint and metal thickness. In the coil coating process, the metal coil is first unwound, cleaned and pre-treated, one or more layers of paint are applied on a flat continuous sheet, heat cured, cooled and rewound for shipment. At the fabricator, it is then cut to the desired size and formed into its finished shape.
Since the metal is first painted and then formed into a part, coil coatings are frequently referred to as pre-paint. Pre-paint refers to the process of painting metal before fabrication rather than painting a formed article. The coated product must not only be able to be cured quickly, it must also be flexible and resistant to pressure mottling as coated coils can weigh several tons.
Compared to most other application methods, coil coating is nearly 100% efficient from a paint usage standpoint. As opposed to a spray-applied coating, a coil-coated product offers uniform film thickness rather than the thicker films on edges, corners and bends that are more typical of spray-applied coatings.
Topcoats are applied by reverse roll coat in which the applicator roll travels in the reverse direction of the strip and thus provides a smoother film with fewer defects. Primers and backers are normally applied by direct roll coating. Some lines also apply coil coatings using an extruder or via a solid block of paint with a softening point such that it can be applied smoothly when heated.
Coil coating physical types include solvent borne, waterborne, powder and solid block paints.
Schematic 1 – Paint layers in a typical exterior surface
Table I – Synopsis of Coil Coating Options
The total global market size of coil coatings is in the range of $3.5 billion (USD) with polyester coatings making up greater than 60% of the total. The types of paint curing employed in the coil industry include thermal, infrared, induction and UV cure. By and large, the vast majority of coil coatings are cured using gas-fired ovens. Accordingly, the remaining portions of this article will focus on thermal-cured coil coatings.
Coil primers and backers are normally applied much thinner than spray-applied liquid or powder coatings, dip or electrocoat paints. Applied primer dry film thicknesses are normally in the range of 4-6 microns, whereas topcoats are normally applied to provide a dry film thickness of 18-20 microns.
Special consideration when formulating coil coatings include adjustments in the resin technology, crosslinking, solvent system, catalyst, surface modifiers and lubricants to accommodate proper cure, flow and leveling, and minimization of surface defects. Once cured, coil coatings can offer excellent handling, physical, chemical and environmental properties. Table II details typical materials utilized in a polyester coil coating.
Table II – Raw Materials (on Resin Solids) used in a Typical Polyester Coil Topcoat (1.2:1.0 Pigment:Binder, Dupont R960 Titanium Dioxide)
In summary, coil coating technology has grown more rapidly than more conventional application technologies and is projected to grow at a rate in excess of 5% per annum due to a variety of benefits that include cost savings, versatility, environmental, performance and quality issues.
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