Stainless steel is one of the most durable materials in the world. Each type of stainless steel has its unique benefits, and we can improve them by applying different types of surface finishes to them.
One such surface finishing technique is stainless steel coating. This technique involves applying a protective polymer to the steel surface to make it more resistant.
Powder Coating Basics.
Powder coating is a surface finish technique that makes your steel more resistant. It is based on the principle of electrostatics. First, you prepare the stainless steel surface for powder coating; then you use an electrostatic gun to spray the powder on it.
The powdered polymer molecules are charged, creating an electrostatic field around them, causing them to stick to the steel surface, which is oppositely charged to the powder particles. You can cure the powder under heat, causing it to melt and permanently stick to the steel surface.
Powder coating is a durable surface finish. It is cost-effective and environmentally friendly. You can get a consistent finish free of any chipping by powder coating.
Powder Coating Options.
The types of powder coating generally can be labeled into three broad classes:
1.Thermoplastic Powder Coating
Thermoplastic materials are materials you can melt and reshape upon heating. This means you can continuously change their shape by heating them.
Using a thermoplastic powder ensures the flexibility of the steel. So, you use them in applications like wire mesh coating, where you don’t want the product to be rigid and immovable.
One example is acrylic powder coating. It is glossy, so you use it for the surface finish of decorative items. Teflon is another common thermoplastic coating that has anti-stick properties. So you use it to coat cutlery to make non-stick pans.
2.Thermosetting Powder Coating.
Thermosetting materials harden when heated, and you cannot repeatedly melt and reshape them. When you heat them, you create a durable chemical bond you cannot physically change.
You use a thermosetting powder coating on stainless steel for applications that requires durability and strength, such as industrial equipment.
One example of thermosetting powder coating is the epoxy coating, which you do to pipes and tanks. Epoxy is a corrosion and chemical-resistant material, so you use it in the chemical industry.
Another thermosetting material is polyester, and it is incredibly weather-resistant. You use it in outdoor applications which are exposed to the weather.
Polyurethane is another thermosetting material that has excellent abrasion resistance. You use it in the automotive industry, where you require excellent impact resistance.
3.Hybrid Powder Coating
Hybrid powder coating refers to combining two powders into one coating. Doing so gives your stainless steel workpiece the properties of both materials. For example, you can combine epoxy and polyester coating to get both weather and chemical resistance. You use this coating in outdoor machinery.
Advantages of Stainless Steel Powder Coating
Powder coating has many benefits: it enhances the visual appeal and stability of the material. Some of these include:
- Corrosion Resistance:. Coating your steel with a suitable material provides it with an extra barrier against corrosive agents. This results in enhanced stability against corrosive forces.
- Aesthetic Appeal:. Different powder coatings enhance your steel’s aesthetic appeal. For example, the acrylic coating gives it a glossy appearance, and the polyester coating can give it a matte look.
- Durability:. Using high-strength materials like epoxy makes your steel more durable. Powdered coatings also protect from damaging UV radiation. Powder coating durability makes your steel last long.
- Chemical Resistance:. Powder coating with chemical-resistant materials can protect your steel from various solvents, acids, and bases that would otherwise deteriorate it.
- Cost-effectiveness:. Powder coating’s cost is significantly less than other surface finishes, like painting or plating.
Limitations of Powder Coating for Stainless Steel.
Despite its many benefits, this technique has some drawbacks:
- Thinner Coating: Compared to alternative methods like painting or plating, powder coating applies a thinner protective layer on the stainless steel surface.
- Limited Size Range: Very large or irregularly shaped objects are difficult to coat, as the standard powder coating equipment isn’t optimized for them.
- Limited Color Range: Compared to painting, powder coating has a significantly smaller variety of colors to choose from.
Applications of Stainless Steel Powder Coating.
Powder-coated stainless steel is used in different industries. For example:
- Architectural Powder Coating:. Powder-coated stainless steel is used in signages and handrails.
- Industrial Powder Coating:. You can use stainless steel coated with chemical-resistant and anticorrosive materials in machinery, equipment, and cools.
- Automotive Powder Coating:. You can use abrasion-resisting material coatings for wheels and grilles.
- Aerospace Powder Coating:. In the aerospace industry, you require heat-resistant powder-coated steel for aircraft engine parts.
- Medical Powder Coating:. A smooth surface finish provided by powder coating is easy to clean and sterilize, making it a good idea to get your surgical instruments coated.
How to Prepare Stainless Steel for Powder Coating
Before you start the powder coating process, you must first make your stainless steel object ready. This involves appropriately cleaning it and watching for any surface defects. Without a prepared and cleaned surface, the powder will not adhere.
Some surface preparation for coating techniques include:
- Abrasive Blasting: This technique blasts abrasive materials like sand on the steel surface to remove dirt and contaminants.
- Mechanical Cleaning: You can use a wire brush to remove contaminants and clean the steel surface mechanically. This technique also creates a rough surface to bind the powder.
- Chemical Etching: In this technique, you use an acid to etch away the surface, creating a textured surface that accepts the powder better.
You must also clean and degrease the steel surface against oils, greases, and contaminants. Use an alcohol or acetone solvent, alkaline solutions, or solvent vapors to do the job.
Surface defects like fish eyes, orange peel, and pinholes can happen if you don’t prepare the steel properly for coating.
The Powder Coating Process for Stainless Steel
The powder coating process for stainless steel takes place in four stages which use different powder coating equipment like a curing oven or a fluidized bed. Here, we discuss each stage:
1.Pretreatment Stage
In the pretreatment stage, you prepare the stainless steel surface for the powder coating process. You must thoroughly remove all oil, grease, and contaminants. At the end of pretreatment, your surface must be clean, dry, and rough to bind powder.
2.Powder Application Stage
You apply the powder through an electrostatic spray gun, fluidized bed dripping, or electrostatic fluidized bed. After this stage, a uniform powder coating is visible on the surface.
3.Curing Stage
You heat the coated steel at a predetermined temperature for a specific time determined by the powder material. The powder will melt and flow over the stainless steel workpiece, producing a smooth, durable finish.
4.Quality Control Stage
Once you apply and cure the powder, you must test its quality. You check for powder adhesion, hardness, and corrosion resistance. You also check for common surface defects. Like orange peel or pinholes.
Common Problems with Powder Coating Stainless Steel and How to Solve Them
Different problems, such as surface defects, can arise due to powder coating. Here are some common problems and how to troubleshoot them:
5.Fish Eyes
Fish eyes are small craters that appear on the surface after coating and are caused by contaminants. If your substrate isn’t properly cleaned, its contaminants will cause a surface tension difference between the surface and the coating, leading to fish eyes.
You can prevent fish eyes by adequately cleaning the surface before powder coating so that all contaminants are removed.
6.Orange Peel
Orange peel refers to a textured appearance after powdered coating, usually due to uneven surface or improperly applying the powder.
To reduce the chances of orange peels, make sure you properly and thoroughly clean your surface from contaminants. You can also adjust the gun settings and reduce the powder application to decrease the risk.
7.Pinholes
Pinholes are small holes in the coating, usually due to air bubbles. You can prevent their formation by adequately cleaning your substrate’s surface. Also, adjust the gun settings and play with the coating speed to ensure air bubbles do not form.
Increasing the curing time also helps with pinholes.
8.Overbaking.
Overbaking happens when your curing temperature is too high or when you cure the substrate for too long, resulting in the powder breaking off or discoloring. Determine the right curing temperature and time, and do not exceed that to prevent overbaking. Use a more heat-resistant powder coating if the problem persists.
9.Under-curing
Under-curing is the opposite of overbaking; it happens due to too less curing temperature or time. Increase the temperature and time to fix this issue.
10.Chalking
Over time, powdery residue appears on your powder-coated stainless steel, known as chalking. Chalking happens due to UV exposure or weathering. This is the natural erosion process of the powder, and you can prevent it by using weathering or UV-resistant powders.
Maintenance and Care of Stainless Steel Powder Coating
Proper powder coating maintenance will increase life. You should regularly clean your coated stainless steel so it does not accumulate contaminants. Clean at least once every week.
Use a mild detergent with hot water, and avoid strong cleaning solutions. Instead of using abrasive cleaners like steel wool, just use a soft cloth. Thoroughly rinse with warm water to avoid streaks and adequately dry the workpiece, or you risk the formation of water stains.
Store your coated stainless steel in a dry place and protect it from moisture. Avoid exposure to harsh chemicals.
It’s also best to ensure you don’t damage the coating. Handle the workpiece carefully, use gloves for delicate coatings, and avoid dragging or dropping the object. Avoid exposing it to high temperatures, as heat can damage the coating.
Environmental Considerations of Stainless Steel Powder Coating
If you are concerned about powder coating sustainability, you can rest easy as it is one of the most eco-friendly and sustainable surface finish techniques. Powder coating generally uses less energy than alternative methods. They produce little material waste, and their durability means you don’t have to replace them for a long time.
However, there are some concerns about powder coating safety during the manufacturing process. The powder coating process can result in the generation of fine particles that can be an inhalation hazard. Likewise, skin contact may sometimes cause allergies, depending on the material. Individuals working in the industry should take all safety precautions and regularly visit their doctor.
Choosing the Best Powder Coating Service Provider for Stainless Steel.
You must contact a reputable service to powder coat your stainless steel.
Consider different factors, like the service provider’s experience and their service’s cost. However, don’t compromise on quality for a lower powder coating cost; instead, extensively inquire about their quality control procedures. Choose a service provider with a low turn-around time so they can meet your project deadlines.
Ask pointed and essential questions, like their experience and the types of coating they provide. Inquire about the warranty of their products. Check their accreditations and ask for references to their previously completed projects.
If they have less or no experience and are unresponsive, that’s a red flag. Likewise, don’t choose providers that offer prices too good to be true. They probably will significantly compromise on quality.
Future of Stainless Steel Powder Coating
Different innovations in the powder coating industry suggest a bright future ahead. The industry will grow as the demand for powder-coated stainless steel increases.
New materials are constantly being developed for powder coating that grant different beneficial properties to the steel. Better spray nozzles are also being developed, providing a more uniform coating to the steel. There is also potential for the development of nanotechnology-based coatings. These improve durability and corrosion resistance by manipulating matter at the nanoscale.
There is also a focus on making the process more sustainable. Eco-friendly options for stainless steel powder coating are continuously being developed.
Endnote
Powder coating is a type of stainless steel surface finish that uses thermoplastic or thermoset materials to provide a layer of protective coating to stainless steel. The process produces a more durable, corrosion and chemical-resistant, and aesthetic steel. The entire process is also cost-effective.
However, you require extreme precision as the process is sensitive, and poor handling can cause issues like pinholes, overbaking, and under-curing. You must also correctly prepare its surface before the process.
The process is environmentally friendly and sustainable. Proper maintenance and cleaning can significantly extend its lifespan. Powder-coated stainless steel is commonly used in industry, architecture, and medical industries.
Contact us today for a quote for premium steel types to powder-coat!
FAQs
1.How long does powder coating last on stainless steel in outdoor applications?
Powder coating generally lasts for fifteen to twenty tears in an outdoor setting. The exact timeframe can vary depending on the environmental conditions and the powder material. Powder coating lasts longer indoors than outdoors due to more stable conditions.
2.Can I apply powder coating to stainless steel at home?
You should not attempt to do powder coating at home. While you can theoretically do it, the process will be highly challenging and risky to do it safely at home. For example, you are at risk of inhalation hazards from the fine particles generated in the powder coating process.
3.What is the difference between epoxy and polyester powder coating for stainless steel?
Epoxy and polyester are both thermoset materials used in stainless steel powder coating but have different applications. Epoxy is generally more durable, hard, and resistant to wearing and cracking, but polyester is more sensitive and suits a low-stress environment more. However, polyester is weather-resistant.
4.What are the benefits of powder coating for medical stainless steel products?
Applying a powder coat can make stainless steel more resistant to corrosion. In medical applications, you require a clean, corrosion-free material, as corrosion can make it difficult to sterilize and clean the equipment properly. Also, a smooth powder coating will result in a material where microorganisms cannot proliferate.
