Is multicolor powder coating possible?

Hello Joe,

I am new to powder coating, but the plant where I work has been doing it for a few years. The guys do a good job on single color and are starting to experiment with multi colors. Is multicolor powder coating possible? If so, do you have any information that would help us?

Thanks

Howard Satterfield

Maintenance Supervisor

Hello Howard,

Thanks for the question. One often overlooked characteristic of powder coatings that sets them apart from liquid paint is that they are discreet fine particles that typically stay that way when they are sprayed. Unlike most liquid paints, mixing two colors don't result in an intermediate color but a blend of individual particles. For example, mixing a red paint and a yellow one of same technology will yield an orange paint. With powder coatings you get a unique speckled finish.

So yes, powder coatings can be mixed. There are many scenarios to consider.

1. Physically blending two or more powders will give you a speckled finish. By mixing an orange, medium brown and a dark brown you can simulate a rust patina. Blends of large-particle textured powder can give the effect you see on roofing shingles. Mixing a light teal green with a black powder will give you a weathered copper look.

2. Some powders are blends of incompatible materials and result in what are commonly referred to as veins and "hammertone" finishes. The veins are comprised of a dry blend of an incompatible powder and a silver or bronze pigment. Hammertones are blends of an incompatible powder with another powder. These are best formulated by the powder manufacturer, however you can experiment with blending various common powders with these veins and hammertones to get interesting effects.

3. Metallics and pearlescents. The simplest technique to create a metallic effect is to blend an already made powder coating with a metallic pigment. Aluminum flakes are most commonly used, but you can also try bronze and stainless steel pigments to create fascinating effects. Concentrations of 0.2 to 5.0 % are typical. Pearlescents are specially synthesized flakes that give a shimmering effect. These can be incorporated just like metallic pigments. Variations of pearls include color shifting flakes that appear as one color at a given viewing angle and another color at different angle.

4. Holographic effects. These are one of my favorites. Microscopic flakes that possess a prismatic effect can be added to powders. Most dramatic effects are realized with darker, more vibrant colors. These holographic flakes are rather expensive but produce a rainbow of colors as you change your viewing angle.

5. Applying dry powder onto another dry powder. Gradient color effects can be achieved by applying one color on part of your target then covering the rest of it with another color. The intersection of the two colors can be quite aesthetically pleasing. Some people have come up with a way to simulate wood grain by spraying multiple dry layers of light and dark brown powders then 'combing' the finish before it sees the oven.

One thing to remember, dry-blends of various powders yield a variable finish. It is difficult to achieve the exact finish repeatedly. Particle size differences between powders and additives and electrostatic variations in application will produce slightly different looks. And reclaimed oversprayed powder will certainly look significantly different than the original blended powders. Keep this in mind if you are trying to coat large parts or long runs of parts.

I would encourage you to experiment with the possibilities. The effects you can create are endless and only limited by your imagination.

Let me know if you have any further questions.

Best Regards,

Joe Powder

Dear Joe,

We have an application were a cast iron component is exposed to a temperature of 560 ⁰C for approximately two hours. Is there a paint product available that can withstand this temperature, not turn dull or blister and still offer good corrosion resistance?

Thanks,

Jim Stevenson

Sales Manager

Hi Jim,

Yes there are powder coatings that can withstand 560 ⁰C for two hours and maintain coating integrity and corrosion resistance. This technology is based on silicone polymers and has been used for years on applications such as gas grills and exhaust parts. They are typically low in gloss to begin with and come in any color you like as long as it's black. Essential to the performance of this technology is the cleaning and preparation of the metal. Conventional phosphate pretreatments unzip at these high service temperatures causing total loss of adhesion. Chromates work, but may be a problem with handling and effluents. Blasting with clean media followed by a rinse and dry-off works quite well.

Proper cleaning and surface preparation of the metal should give you at least 500 hours of salt spray resistance.

Best Regards,

Joe Powder

Hello Joe,

I'm in the powder coating business and I found your name while looking for the best way to dispose of unused powder. I just want to be sure we are up to date with the latest methods. Thank you for your help.

Best Regards,

Diane Stern
United States

Hi Diane,

Here's what I think - I owned and operated a powder coating manufacturing company in Columbus, Ohio, for a few years. Occasionally we would generate a small amount of unusable powder. We would simply double-bag it, place the bag in a heavy box or drum and toss it into the dumpster destined for the landfill. Here are a few very important recommendations however:

1. You must be 100% certain that the powder you are disposing contains no toxic materials. Consult the safety data sheet (SDS) provided by your powder supplier to ascertain this. Even better, personally contact your supplier to ensure there are no toxic materials present.

2. Secure the powder in a container that is durable enough to withstand the pick-up, transport and delivery into the land-fill. Most waste haulers are concerned when a package breaks, creating a dusty plume.

3. Before you do anything, contact your waste hauler. It is their job to know the local and national regulations concerning the acceptability of waste product disposal. Local laws vary, so my experience in Columbus, Ohio, may not apply to your location.

4. If your powder contains toxic materials you should follow the guidelines for disposal per the SDS provided by your powder supplier. This may involve contracting a hazardous waste handler and the high costs associated with using one.

For more information regarding US regulations you can review 40-CFR261 (code of federal regulations) that cover solid wastes per the RCRA (Resource Conservation and Recovery Act). This is easily accessed on-line at http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&tpl=/ecfrbrowse/Title40/40cfr261_main_02.tpl . Other jurisdictions certainly have their own regulations as well.

The vast majority of powder coatings are nontoxic and safe to dispose in a landfill. But before doing anything, be prudent and confirm this with your local authorities. Hopefully your costs and efforts will be minimal.

Best Regards,

Joe

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