Corona Treatment FAQ

Corona treatment is a surface modification process that uses a high-frequency, high-voltage electrical discharge (also known as corona discharge) to increase the surface energy (or dyne level) of a material. This makes the surface more receptive to inks, coatings, adhesives, and laminates.

When a film, foil, or other substrate passes through the corona discharge field, the electrical energy breaks molecular bonds on the surface and introduces polar functional groups (primarily oxygen-containing groups). This raises the material’s surface energy and dramatically improves adhesion.

Corona treatment is widely used in printing, packaging, coating, laminating, and film extrusion to ensure consistent, reliable adhesion.

Surface energy is a property of a material’s surface that determines how well it will bond with inks, coatings, adhesives, and laminates. It is measured in millinewtons per meter (mN/m) and reflects the degree to which a surface is chemically active and ready to form a strong bond.

Surface free energy is composed of two components: dispersive and polar. Dispersive energy is present in all materials and relates to Van der Waals forces — weak, non-specific molecular attractions. Polar energy arises from stronger, directional molecular interactions such as hydrogen bonding and dipole forces. For strong, durable adhesion, polar energy is a critical factor.

Most plastics and films—including polyethylene, polypropylene, and PET—are inherently low surface energy materials that are almost entirely dispersive. Their surfaces lack the polar functional groups needed to interact strongly with polar inks and adhesives. This is why they are notoriously difficult to print and coat without pre-treatment.

Corona treatment changes this by exposing the substrate surface to a high-frequency electrical discharge, which breaks molecular bonds at the surface and introduces polar functional groups—such as carbonyl, hydroxyl, and carboxyl groups—directly onto the substrate. This shifts the surface chemistry from predominantly dispersive to a healthier balance of dispersive and polar energy, dramatically improving its compatibility with polar inks, coatings, and adhesives.

Think of it this way: water beads up on an untreated polyethylene film because the surface is dispersive and has no affinity for the polar water molecule. After corona treatment, the same film will wet out completely. The introduced polar groups attract and interact with the water, just as they will with your ink or adhesive in production.

Dyne level and surface energy are related concepts, but they are not the same thing, and confusing the two can lead to adhesion problems that are difficult to diagnose.

Surface energy is a fundamental property of the solid substrate, measured in millinewtons per meter (mN/m). It describes how chemically active the surface is and how readily it will interact with inks, coatings, and adhesives. Surface tension is the equivalent property of a liquid—it describes how much a liquid resists spreading. Dyne level is a practical measurement of a substrate’s wetting tension: the point at which a dyne solution of known surface tension just barely wets the surface.

In practice, dyne level is used as a quick compatibility check. If you know the surface tension of your ink or coating, you can use dyne solutions to confirm that your substrate will wet out properly.

However, dyne measurements have limitations. A substrate can test at the correct dyne level but still fail in adhesion. Due to outlying factors like surface contaminants that go undetected in dyne measurements. This is why contact angle measurement provides a more complete picture when troubleshooting adhesion failures.

There are two primary methods for measuring surface energy: dyne testing and contact angle measurement.

Dyne testing uses solutions of known surface tension to assess whether a surface is ready to bond with inks, coatings, or adhesives. It’s fast and widely used in production environments, but results are subjective and operator-dependent. Dyne solutions can also cut through surface contaminants—such as migrated slip agents—producing false positives. A substrate may pass dyne testing but still fail in real-world adhesion applications.

Contact angle measurement is the more precise alternative. By analyzing how a liquid droplet interacts with a surface, it calculates surface free energy and separates it into its polar and dispersive components, giving a far more complete picture of surface chemistry. Modern instruments automate the process, eliminating operator subjectivity and producing highly repeatable, quantitative results.

For production monitoring, dyne testing offers a quick check. For troubleshooting, quality assurance, or any application where accuracy matters, contact angle measurement is the more reliable choice.

At QC Electronics, we use a KRÜSS Mobile Surface Analyzer (MSA) in our test lab to perform contact angle measurements on customer substrates. The MSA automates droplet dispensing and contact angle capture, calculating surface free energy—including its polar and dispersive components—with high accuracy and repeatability.

This allows us to provide quantitative, objective data when evaluating your material’s adhesion readiness or troubleshooting a treatment problem. Rather than relying on a pass/fail dyne test, we can tell you exactly what your surface energy is, how it’s composed, and what treatment level is needed to achieve optimal adhesion for your specific application.

If you’d like us to test your substrate, contact us to arrange a free lab evaluation. We’ll treat your material and send back a full surface energy report. No cost, no commitment.

Watt density is the amount of power applied per unit area of substrate, expressed in watts per square foot per minute (W·min/ft²) or watts per square meter per minute (W·min/m²). It is the primary variable you control to achieve a target dyne level.

Watt density is calculated as: Power (W) ÷ (Treating Width × Line Speed x Treat Sides (1 or 2)). QC Electronics provides a free watt density calculator on our website to simplify this for your process.

Applying too little watt density results in under-treatment (poor adhesion); applying too much can cause over-treatment, which also has adverse effects. Our engineers can help you dial in the right setpoint for your specific substrate and line speed.

Corona treatment is effective on a wide range of non-conductive materials, including:

• Polyethylene (PE) and polypropylene (PP) films
• Biaxially oriented films (BOPP, BOPET, BOPA)
• PET and PVC films and sheets
• Aluminum foil and metallized films
• Paper and paperboard
• Nonwoven fabrics
• Rubber and elastomers
• Specialty films for medical and food packaging

Conductive substrates like aluminum or metallized poly cannot be treated with a covered roll system but can be treated with a conventional bare roll configuration. Not sure which configuration is right for your material? Contact our team or send us a sample for lab testing.

Both corona and plasma treatment use electrical energy to modify surface chemistry, but they differ in how and where they’re applied:

• Corona treatment operates at atmospheric pressure, making it ideal for high-speed web processing in converting, printing, and extrusion lines. It is the most cost-effective and widely adopted surface treatment method in flexible packaging.
• Plasma treatment can be atmospheric or low-pressure (vacuum). Atmospheric plasma offers more targeted treatment and can be used on three-dimensional shapes or difficult substrates. Low-pressure plasma provides more uniform treatment depth but requires a vacuum chamber, limiting throughput.

For most film, foil, and web applications, corona treatment is the preferred solution due to its speed, cost efficiency, and proven reliability. QC Electronics also offers plasma treatment systems for specialty applications — contact us to discuss your requirements.

Bare Roll Corona Treaters use a grounded metal roll (optionally coated with our proprietary ceramic coating for extended longevity) with a set of high-voltage ceramic electrodes positioned above the ground roll. The substrate passes through the gap. This configuration is ideal for both conductive and non-conductive materials like plastic films, paper, and foil in converting applications.

Covered Roll Corona Treaters use a ground roll coated with a dielectric material (ceramic, silicone sleeving, or epoxy). It is the preferred choice for blown and cast film extrusion lines where only non-conductive substrates are treated. QC Electronics’ TNT covered roll treater offers blown and cast film extruders a 50% increase in efficiency compared to conventional bare roll systems.

The right choice depends on your process, substrate, and line configuration. Our engineering team can recommend the best fit — request a quote to get started.

For blown and cast film extrusion, a covered roll corona treater is the standard choice.

QC Electronics’ TNT Covered Roll Corona Treater is purpose-built for blown and cast film applications, offering single- and double-sided treatment options, ceramic, silicone, and epoxy coating options, and proprietary technology that absorbs splice impacts and prevents electrode head re-adjustments upon mechanical impact — a common failure mode in competing systems.

Key specifications to share when requesting a quote: treat width, line speed (FPM/MPM), substrate type and thickness, and target dyne level. If you are unaware of your target dyne level, our team is fully equipped to specify that for you.

Narrow web corona treaters are designed for label printing, flexible packaging, and other converting processes on narrower web widths — typically up to 24 inches. They integrate directly into flexographic printing presses to treat labels, films, and specialty substrates inline before printing.

QC Electronics’ Advantage Narrow Web Corona Treater features watt density control, HMI touch interface options, and full customization for single- or double-sided treatment. It is engineered for seamless integration with any press configuration.

Yes. Every QC Electronics corona treater is built to order, and we specialize in custom configurations. Whether you need an unusual treating width, a specific electrode geometry, integration with existing equipment, or treatment of an unconventional substrate, our engineering team will design a solution for your exact application.

Visit our Specialty Applications page or contact us to discuss your requirements.

Yes. QC Electronics offers system upgrades and retrofits for aging corona treatment equipment, including generator upgrades, control system modernization, electrode assembly replacements, and roll reconditioning. In many cases, upgrading existing equipment is more cost-effective than full replacement.

Contact our engineering team with your current equipment details to explore upgrade options.

In most cases, yes. UV and water-based inks have a higher surface tension than solvent-based inks, which means the substrate must have a sufficiently high dyne level for the ink to wet out and adhere properly.

Untreated polyolefin films are particularly challenging for UV printing. Corona treatment raises the substrate’s surface energy to ensure proper ink adhesion, preventing issues like ink crawling, poor bond strength, and delamination.

If you’re experiencing print quality issues on plastic films, our free lab testing service can diagnose the problem and recommend a treatment protocol.

Corona treatment is considered an essential process step in flexible packaging manufacturing. Whether you are printing, coating, laminating, or applying adhesives to polyethylene, polypropylene, PET, or metallized films, corona treatment ensures the surface energy of the substrate is high enough for reliable adhesion throughout the product’s shelf life.

Without adequate treatment, flexible packaging is at risk of ink delamination, coating failure, and laminate separation — which can lead to costly product recalls and customer returns.

Yes. Corona treatment is widely used in medical device packaging, pharmaceutical blister packaging, and food packaging film production. The treatment process itself does not introduce chemical residues to the substrate — it modifies only the outermost molecular layer of the surface.

QC Electronics corona treaters are CE certified and built to meet the demands of regulated industries. Our engineering team can work with you to document your treatment process for validation and compliance purposes. Contact us to discuss your specific requirements.

Yes, though paper and paperboard already have relatively higher surface energy than plastic films. Corona treatment of paper is used primarily to improve print quality, enhance coating adhesion, and prepare surfaces for lamination. It is also used on release liners to ensure consistent adhesive peel performance.

For paper applications, our engineering team will help you determine the appropriate watt density and electrode configuration to avoid over-treatment, which can cause surface degradation in some paper grades.

QC Electronics recommends cleaning ceramic electrodes every 500 hours of operation, or during any job change or scheduled downtime. Use lint-free rags dampened with isopropyl alcohol (IPA) and gently scrub with a Scotch-Brite pad if buildup is present.

Keep the electrode face free of plastic residue, adhesive, and other contaminants. Carbon buildup on electrode wires and insulators can cause arcing and high-voltage trips, so regular cleaning is critical to reliable operation.

Refer to our Support page for full cleaning procedures.

A high-voltage trip is indicated by a Red → Amber/Green → Green → Red LED sequence that repeats continuously. The most common causes are:

• Electrode wires too close to ground: After installing new electrodes, ensure all wires have at least 1.5″ clearance from any grounded surface or control wiring.
• Pin-holed electrodes: Violent arcing at a consistent spot on one electrode indicates a pin hole. Disconnect electrodes one by one to isolate the failed unit.
• Carbon tracking on insulators: Teflon and G10 insulators can develop conductive carbon tracks over time. Affected components must be replaced. Ask us about our trackless insulator assemblies, which eliminate this issue.
• Condensation inside the treating head: On humid days, run the blower for 20 minutes before production, or run the unit at a low KW setpoint for 30–40 seconds to evaporate moisture.
• Pin-holed ground roll coating (covered roll systems): If the high-voltage trip occurs at the same rotational position on the roll, the coating is likely pin-holed at that spot.

For after-hours emergencies, call 608-742-1661 to reach our on-call engineers 24/7.

To minimize unplanned downtime, QC Electronics recommends keeping the following spare parts readily available:

• Bare Roll Advantage Treater: At least two spare ceramic electrodes (depending on system size); one power supply spare parts kit.
• Covered Roll TNT Treater (silicone sleeve): Spare silicone sleeving; one power supply spare parts kit.
• Covered Roll TNT Treater (coated roll): One spare coated ground roll—without a spare you may be down for weeks waiting on a strip and recoat; one power supply spare parts kit.

Contact sales@qcelectronics.com to order spare parts kits, consumables, and replacement electrodes.

Ceramic electrodes should be replaced when you observe any of the following:

• Visible pin holes (points of localized, violent arcing)
• Cracking or chipping of the ceramic body
• Inability to achieve adequate dyne level at normal power settings
• Repeated high-voltage trips traced to a specific electrode

QC Electronics maintains a large inventory of stock ceramic electrodes for fast turnaround. Visit our Ceramic Electrodes page or contact us to find the right replacement for your system.

Wipe the roll surface with lint-free rags dampened with an appropriate solvent: isopropyl alcohol (IPA), methyl ethyl ketone (MEK), naphtha, or trichloroethylene (TCE) depending on what needs to be removed. Gentle scrubbing with a Scotch-Brite pad is effective on stubborn buildup.

Critical: Never soak the surface with liquid, as it can penetrate the coating and cause arcing if conductive. Always allow the surface to dry completely before applying power. Test your approach on the edge of the roll outside the web path first.

Clean coated rolls every 500 hours, or during job changes and scheduled downtime.

Use Mobilith SHC 100 grease on corona treater ground roll bearings. Do not mix greases — mixing different grease types can degrade lubrication performance.

Grease the zerk fittings according to your operating environment:

• Clean environments: every 12 months
• Dirty environments: every 6 months
• Washdown or extremely dirty environments: every 3 months

Also inspect and replace the ground brush on the exhaust (EX) end of the ground roll every 500 hours.

Yes. QC Electronics provides 24/7 emergency support to all QC corona treater customers. Call 608-742-1661 at any time to be connected with an on-call engineer who can help diagnose and resolve your issue — often without an on-site visit.

Our treaters are also designed for remote diagnostic access, so our service engineers can identify and troubleshoot problems quickly and efficiently from our facility in Portage, Wisconsin.

All QC Electronics corona treatment systems are designed and manufactured at our facility in Portage, Wisconsin, USA. We maintain full control over our manufacturing process—from steel fabrication and welding to electrical assembly and final quality testing—ensuring the highest standards of build quality and reliability.

Every unit is tested before it leaves our facility. Manufacturing in the USA also means faster lead times, easier customs for domestic customers, and direct access to our engineering team throughout the sales and support process.

Yes. QC Electronics offers free lab testing to new and existing customers. Send us your substrate samples and our expert lab team will treat them on our in-house equipment, analyze the results using KRUSS material characterization instruments, and provide you with a detailed treatment report and consultation.

This is particularly valuable when evaluating a new substrate, troubleshooting an adhesion problem, or verifying that corona treatment will meet your application requirements before investing in equipment.

To request lab testing, contact us at sales@qcelectronics.com or visit our Lab Testing page.

Contract corona treatment (also called toll treatment) allows you to have your materials professionally corona-treated at QC Electronics’ facility without owning your own equipment. This is ideal for:

• Companies evaluating corona treatment before purchasing a system
• Processors with occasional treatment needs that don’t justify capital equipment
• Situations where an in-house treater is down and production must continue

QC Electronics operates a double corona treater line with both the Advantage and TNT models available. Learn more on our Contract Corona Treatment page.

Yes. QC Electronics corona treaters carry CE certification, confirming conformity with applicable European health, safety, and environmental protection standards. CE certification is required for equipment sold into the European Union and is increasingly requested by multinational manufacturers worldwide as a mark of quality and regulatory compliance.

To provide an accurate quote, our engineering team will need a few key details:

• Treating width (inches or mm)
• Line speed (feet per minute or meters per minute)
• Substrate type and thickness
• Target surface energy or dyne level (if known)
• Single- or double-sided treatment requirement
• Power supply voltage available (120V, 240V, 480V, etc.)
• Integration requirements (new line vs. retrofit)

Visit our Request a Quote page to submit your details, or call us directly at 608-742-1661.