Monthly Archives: April 2016

Using Iron Phosphate To Get A Better Powder Coated Finish

Pic for steam unit pageWe’ve talked a lot about pretreatment in previous articles: why it’s important to get your parts clean and what pretreatment options you have. But from a production standpoint, why is pretreatment important? Why add another step to your powder coating process? We’ll examine this using one of the most commonly powder coated materials: steel.

If you are powder coating, chances are that at some point you’ll be powder coating steel. Powder is easily applied to steel parts and generally provides a good finish. But what if you need the powder coating on your steel parts to last longer or to be more wear-resistant? You may be providing parts that will be subject to high-impact or are handled regularly, or parts that must last a certain amount of time. Simply applying the powder and curing the part won’t achieve the result you or your customers need. In order to get those results, you’ll need to add a pretreatment step before you apply the powder.

One of the most popular and effective forms of pretreatment for steel is iron phosphate. Iron phosphate is a conversion coating that provides a barrier against oxidation. It is most effective on bare (uncoated), clean steel.

How Can Iron Phosphate Improve My Powder Coated Finish?

Adding an iron phosphate stage to your pretreatment can dramatically improve the quality and longevity of your powder coating.

Iron phosphate provides increased adhesion. This is especially useful for slick surfaces. Iron phosphate pretreatment causes a small amount of surface material to be deposited on the parts being treated. This material is slightly textured so the powder can grip it. If the parts are occasionally bumped during their use, this improved adhesion is especially helpful because it keeps the coating intact.

Iron phosphate provides increased corrosion resistance. Most powders provide a salt-spray rating of 250 hours on clean metal, but what happens when the protective powder coating is scratched or worn? Phosphate adds a second layer of protection and can extend the salt-spray rating to 500-1500 hours, depending on the process.

How Can Iron Phosphate Be Applied?

There are a number of different ways to apply iron phosphate to your parts before you apply the powder coating.

Hand wipe: While not very efficient or consistent, there are chemicals that can be hand wiped on and then rinsed off to form an iron phosphate layer.

Hand spray: Professional quality wand systems, also known as spray wands, are very good at delivering iron phosphate chemicals to the surface of most parts. Iron phosphate works well with heat, so gas fueled or electrically heated sprayers work best. These sprayers may include pressure wash, wet steam or dry steam features. A rinse/seal step is often required as part of the process to prevent streaking or chalking that can interfere with the powder coating. Spraying is often done inside a stainless steel booth, often called a manual wash station, and/or may take place over top of a grated wash stage that allows spent chemistry to be contained and potentially recycled.

You can see a hand-operated spray wand in the video by Electro-steam below:

Dip: Heated chemical vats, also known as dip tanks, are a great way to pretreat baskets of small parts that have hard to reach areas. This often involves multiple stages performed in a series of tanks with rinse stages in between.

Automatic spray: This is generally the most effective and consistent way to apply iron phosphate chemistry, but it is also the most expensive. Multi-stage spray systems are typically part of an automated coating line where the parts travel by conveyor at a pre-set rate. A multiple stage pretreatment system can have as few as 2 stages or as many as 8 or more stages. For higher-end architectural finishes, multiple applications of phosphate create an excellent corrosion barrier and other agents in the chemistry clean the part to allow for nearly defect-free parts when powder coating is applied.

Where Can I Find An Iron Phosphate Supplier?

Search online for companies like Bulk Chemicals, Chemetall, Dubois, or Houghton. These companies and others can provide you with information about local suppliers or will have a local distributor contact you to help you select the proper chemicals.

Your local powder supplier can suggest a chemical supplier who will have products that work well with the powders you are using.

Thomas Register & related industry guides may also be able to provide you with an iron phosphate supplier. You can get a lot of information from industry guides like Thomasnet.com, but you may have to play around with your search settings to find companies that will do business on a smaller scale.

As a general rule, avoid online outlets that cater to the hobbyist and DIY markets. They may have chemical products of inferior quality or from sources that vary from batch to batch. Parts preparation is one of the most important steps in the coating process—don’t risk costly reworks by using cheap, no-name chemistry sold online by the bucket.

Have any questions on pretreatment? Need to add pretreatment to your powder coating operation? Reliant provides blast rooms and wash stations for use with your existing equipment, or we can implement your pretreatment requirements into the design of your new coating system. Whatever you need, from hand-wash spray units to fully automated wash stations, Reliant Finishing Systems can provide a quality system at an unbeatable price. Call one of our system specialists today to get started.

 

How A Powder Coating Oven Recorder Can Help Solve Your Curing Problems

Powder Coating ovens from Reliant Finishing SystemsWhether you’re just starting to powder coat or your powder line has been operational for years, you need to have an accurate picture of what’s going on inside your curing oven if you want the best results. Fortunately, there are a number of maintenance and troubleshooting tools available to help get the best finishes possible from your coating equipment. One of these tools is a powder coating oven recorder, also known as an oven data recorder, which can help identify curing problems, increase your throughput, and optimize your oven’s fuel efficiency.

When Should I Use A Powder Coating Oven Recorder?

When first starting to powder coat, it is a good idea to run an oven data recorder to determine exactly how fast your metal parts reach the proper powder curing temperature. This is important because powder companies formulate their powder to cure with specific metal temperatures and curing cycles in mind.

Depending on your market and your customer’s specifications, you may want to run a powder coating oven recorder whenever you add a new type of powder to your process. You may also want to check the oven’s performance if you are working with parts that are much heavier, thinner, larger or smaller than usual, or made of a different material (such as swapping to aluminum from steel). This is especially important if your customer has stringent finish requirements.

Identifying Powder Over-Bake and Under-Bake

The primary reason for checking your metal temperatures is to make sure you are not over-baking or under-baking your powder. Over-baking usually refers to curing the powder at higher than recommended temperatures, while under-baking means the opposite. These terms are also used when talking about the amount of time that the part surface is at curing temperature. Too long can cause over-baking and too little can result in under-baking.

Over-baking powder can lead to brittleness, flaking, discoloration (yellowing or browning), and lack of gloss. Under-baking powder can cause excessive orange peel, poor chemical resistance, lack of adhesion, inconsistent gloss, and poor resistance to corrosion. If your powder is exhibiting any of these problems, it may indicate that your oven is getting too hot or not getting hot enough. An oven recorder can help identify if your oven temperature (https://www.reliantfinishingsystems.com/powder-coating-equipment/powder-coating-ovens/) is not reaching the desired range or if there are hot spots or cold spots in the cabin that are impacting your curing results. If the temperature in the oven is not within the necessary range, or it is significantly inconsistent inside the cabin, you’ll end up dealing with curing problems even if they are not immediately detectable. A high quality powder coating oven recorder is the best tool to use when you need to identify those issues.

Understanding An Oven Data Recorder Report

There are a number of oven recorders on the market, but the most well-known brand used in the finishing industry is Datapaq. Their oven reporting software is what we will be referencing for this article. Here is a typical Datapaq graph and printed report:

Powder Coating Oven Recorder Report - Graph

Powder Coating Oven Report - Technical Readout
That is a typical report from a walk-in size batch powder coating oven from Reliant Finishing Systems. The first thing to look at is the graph itself:

Powder Coating Oven Recorder Report - Graph Close-up
The top red line shows the air temperature probe, which measures the air temperature of the oven at a specific location, usually near the part being tested. At arrow A, the air temperature rises to the 425° F set point (the temperature that the operator wants the oven to reach) and then starts idling at +/- 5 degrees. This consistent discharge of heated air allows the metal temperatures, arrow B, to rise evenly to the desired curing temperature.

If you notice dips in the air temperature line, these represent potential problems that can hurt your throughput by increasing cure times, and may reduce your overall finish quality. This is because undesired drops in air temperature may decrease the consistency of the surface temperature of the part.

The opposite problem, spikes in the air temperature, can be just as bad. Whenever your oven’s heat system overshoots the temperature you want, you’re wasting fuel. You can also end up damaging finishes that require a delicate touch. By not recognizing the way excessive air temps influence your curing cycle, you’re also probably not operating at maximum throughput.

Some common causes of poor temperature regulation by the oven’s heat system include bad temp probes (thermocouples), insufficient insulation or insulation that has settled inside panels during shipment or handling, poor air circulation through the oven cabin, improper exhaust ventilation airflow, inadequate ducting, and faulty or outdated controls.

In batch operations, employees opening the oven randomly during the curing process to check the parts can dramatically affect the air temperature inside the oven and can lead to improper curing. Obviously, opening the doors lets out hot air but the rapid drop in temperature can also cause the oven’s heat system to go into overdrive getting the temperature back to the desired range. This wastes gas. Once the doors are closed again, the overshoot can cause the oven to overheat because the heat system cannot throttle back quickly enough once the hot air is no longer escaping from the cabin.

Using Your Oven Data Recorder On An Automated Line

When testing automatic coating lines, the powder coating oven recorder travels through the oven on the conveyor. It is not unusual to see temperature fluctuations around oven openings, during direction changes near the ends of multi-pass ovens or when the recorder gets close to the output of the heat system. Adjustments to air distribution baffles, plenum discharge dampers or exhaust intakes are typical when fine-tuning an automated line.

Here is an example of an automatic line test. This graph shows some serious temperature fluctuations:

Powder Coating Oven Recorder - Automated Line Test
Although not in color in this example, the two jagged top lines indicate the air temperatures measured as the recorder moved through the oven. The two smoother lines indicate metal temperatures. You can see how the abrupt drop in air temperature affects the metal temperature graphs. This can extend the dwell time needed in the oven, requiring a lower line speed for proper curing. Left unchanged, this can cause uncured parts to reach packing. A problem of this type with a conveyorized powder coating system may be due to a faulty burner in one of the heat units or perhaps a brief burner shut-down due to a safety switch tripping.

The powder coating oven recorder report gives you a couple charts showing the temperatures achieved and the time above these temperatures.

Powder Coating Oven Recorder - Automated Line Technical Readout

The arrow shows the cure time needed for the cure temperature specified. You can get this information from your powder supplier. The times circled are the metal parts’ time above the required curing temperature. Since these times are greater than the specified duration at the curing temperature, the parts should be fully cured when they exit the oven. If they do not reach the specified time at temperature, you’ll probably have to turn up the temperature of your oven or increase the dwell time.

Different metal thicknesses will affect your cure temperatures and times. If you are curing thin and thick parts at the same time using the same time/temp combination, you can possibly over-bake the thin parts–causing discoloration or reduction in gloss. Try to batch similar thicknesses of parts whenever possible. It’s also a good idea not to mix aluminum, stainless and mild steel parts if possible because they can have different curing characteristics. Even if you don’t use a data recorder, make sure you check the finishes you are getting with samples of all of your common parts when setting up your oven. Don’t let lack of attention to detail during set-up rob you of future profits.

When To Call In The Pros

Many powder providers will be glad to run a data recorder through your oven and share the information they discover. This allows them to help you get the best results from their products. It also gives them a chance to justifiably blame bad finishes on faulty or poorly calibrated equipment.

Larger production facilities and high-end job shops may have their own data recorders. These are usually stored and operated by finish line managers or facility maintenance technicians. In smaller shops, owners may have to request a line audit from a service company.

No matter who runs the data recorder, adjustments to the oven should usually be made by factory-authorized technicians. Shops with large coating lines may have in-house personnel trained to repair and adjust their ovens by the manufacturers or providers. That situation is uncommon, and most powder curing ovens are supported directly by the oven manufacturer, an equipment distributor or a specialized service company. When it comes to tuning your oven, we recommend that (whenever practical) you work with the company that built it.

Your powder coating oven should be started and calibrated by an experienced professional. Ideally, you should run some test parts with a data recorder early-on. After you’re in production, it is a good idea to check your oven quarterly or whenever you have a new part with significantly different thicknesses or geometry. A properly cured part is essential for your customers’ long-term satisfaction and will prevent costly returns and reworks.

Need your oven checked? Reliant Finishing Systems offers a wide array of services, including oven data recording, technical support, line audits and other troubleshooting services. Give us a call today.

Powder Coating Special Effects Can Give You Outstanding Results

Powder Coating Special Effects

Examples of powder coating special effects, provided by Espo’s Powder Coating.

As you know, powder can give you a more vibrant finish that lasts longer than traditional wet paint, and now it can rival wet paint’s ability to create jaw-dropping special effects. Many people, including coaters who have worked exclusively in a production environment, are sometimes unfamiliar with the effects that can be achieved with powder coating. In this article we’ll discuss some of the amazing powder coating special effects you can achieve with today’s powder coating technology.

Difference Between Powder Coating & Wet Paint Effects

While powder coating special effects are similar to wet paint, there are some key process differences between the two applications. Wet painters frequently use multiple layers of paint that are combined to create depth and brilliance. Liquid painters also use products that have specialized metallic or mica pigments to reflect light. These products can be applied in separate coating steps to create a custom look.

Powder coating special effects works in a similar fashion, but you have to cure, or at least partially cure, each powder layer before applying the next coat to achieve the correct results when attempting process special effects. Although this can be time consuming, you can get amazing results from multi-step effects like candy-coats and two-tone finishes.

Like certain wet paint products, there are powders that can create one-step special effects. Popular one-step effects include river textures, wrinkle textures, hammer-tone, veining, glimmer, and even holographic finishes. These one-step finishes just need to be applied carefully and evenly to your metal surface and then cured per the suppliers’ recommendations.

Process Powder Coating Special Effects

A process special effect is a special powder coated finish that can only be applied with multiple powder applications and curing steps. This includes candy colors and two-tone finishes.

Candy Colors, also known as candies: These products create finishes that have incredible depth and usually provide bright, dramatic colors. They are typically applied in 3 steps: a metallic primer provides the background, then a transparent but colored base coat is applied, and then a clear gloss topcoat completes the effect. Each coat is cured individually. The final clear is not always required, but will add durability and protection for exterior parts.

Prismatic Powders has a great example of a header done with one of their finishes here: http://www.prismaticpowders.com/gallery/detail/8296/Prismatic-Illusion-Violet-with-Clear- Vision-Top-Coat/

Two-Tone Finishes, also known as bi-tone or cut color:  A two-color finish that requires masking, and requires skill and patience to achieve the desired result. Masking a powder effect is challenging and you need to use high temperature tape in order to keep a clean line between colors. Using two colors that are intense and dramatically different will give you the best results because the second color coat usually has to cover the first coat. It can be done with some transparent coatings, but you will have to carefully plan your finish order. Like with anything you powder coat, doing small test pieces is always recommended before finishing large production pieces.

TIP: When removing high-temp masking tape, try to do it when the part is around 180° to 200°F. If you wait until it’s cooled down to room temperature it can leave flakes. If you pull it too early and the part is still near curing temperature it can pull strings of applied powder off of the surface of the part. A hand-held heat gun and a good quality IR thermometer (temp gun) can help with this custom technique by heating the part if it gets too cool and preventing damage to the finish.

Tom Esposito of Espo’s Powder Coating did a fantastic blending job using no tape to produce this custom frame finish: Powder coating special effects examples from Espo’s Powder Coating

One-Step Powder Coating Special Effects

As opposed to process effects, one-step effects are sprayed and cured just like conventional powder. All major powder manufacturers have special effect finishes that can be sprayed on in one step and then cured. The most common powder coating special effects are those that create textured finishes. Wrinkle and river are some of the terms used to describe the visual effects these powders create.

It is important to note that these powders must be mixed consistently to achieve consistent results. Conventional vibratory box guns are not as effective as hopper style guns that feature hoppers with fluidizing membranes. These hoppers constantly mix the powder with air, while vibratory box-fed guns may separate the heavier particles from the lighter ones due to agitation (think of the way gold panning works). Light textures usually work fine, but the heavier veining effect powders with multiple metallic or mica flakes can give disappointing results when sprayed from a box hooked to a vibratory gun system.

Vein/River Texture: Vein textures are quite dramatic and can give a unique look to your parts. They are often used for electronic enclosures, interior industrial applications, and many interior furniture components. Be careful selecting a vein for an outdoor application. Because of the nature of the veined powder, it can cause different finish thicknesses across the part and may compromise the salt-spray durability of the powder. Unless a texture effect powder product specifically states that it is for outside use, consider it as interior-use only.

Here is a Cardinal Powder chart that shows some different vein effect powders that are available: http://www.cardinalpaint.com/products/productcat.php?pcid=2&cctid=12

Metallics: True metallics come in two qualities: bonded and unbonded. Bonded metallics have a little bit of clear powder attached to the metallic powder particles and may be suitable for one-step interior applications. Unbonded metallics need to be coated again with a clear topcoat to protect the metallic particles from oxidization. Some bonded metallics also need an extra clear coat for exterior durability.

TIP: Metallic effect powders sometimes need different gun settings due to their conductivity. If you get weird patterns when spraying metallics, turn down your kV setting to the 20 to 40 range and see if that helps.

Micas: These specialty powders create finishes that look similar to metallics but are more pearlescent or opaque. They can be used on interior or exterior parts and are typically cheaper than the bonded metallic effect powders.

Hammer-Tones: These powders usually combine the river effects with pearlescent mica pigments. Consistent film thickness is important to maintaining a consistent hammered finish appearance.

As you can see, powder coated finishes can offer impressive custom looks. Modern powders can produce a wide range of special effects that can take your project to the next level.

Have you used any of these powder coating special effects before? Especially proud of your work? Even if you don’t use equipment from Reliant Finishing Systems, send your pics to info@reliantfinishingsystems.com so we can share your work with others who have an interest in powder effects.

You can also share them on our Facebook page at www.facebook.com/reliantfinishingystems