A Guide to Corona Treatment for Printing: Boosting Surface Energy for Better Results

In flexographic printing, print quality is not determined by ink alone — it starts at the substrate surface. Many non-porous materials, such as polyethylene (PE) and polypropylene (PP), naturally resist ink adhesion, leading to peeling, smearing, and costly rejected batches.

Corona pretreatment is a surface activation process used before printing to increase surface energy, allowing inks, coatings, and adhesives to bond reliably with plastic films.

How Does Corona Treatment for Printing Work?

Several materials used in flexo printing have nonporous surfaces. Plastic films, foil, and cellophane are some examples. Ink adherence is difficult when materials are made from polyethylene and polypropylene. These nonporous surfaces have low dyne energy, which makes them non-receptive to printing ink, adhesives, and coatings. This is where corona treatment in printing comes in. This surface activation process of these nonporous materials makes them susceptible to flexo printing. 

Preparing the Substrates for Corona Printing

Corona treatment for printing is essential in preparing the substrates for flexo label printing machines. The corona pre-treatment is a surface preparation treatment to prep the label substrate before ink is applied. 

This pre-treatment solution is recommended for narrow web industry output such as stickers, small packaging labels, plastics, and small packaging. 

The corona pre-treatment prepares the flexo printing press by priming the substrate. This results in edge-to-edge adhesion, UV ink compatibility, and speed matching. The corona pre-treatment is recommended for synthetic films such as BOPP or PET. 

BOP means Biaxially Oriented Polypropylene, which is a high-grade plastic film stretched in two directions to make it more durable, clearer, and thinner. BOP is waterproof, oil-resistant, and chemical, which makes it an ideal candidate for corona treatment in printing. You can find these types of materials in snack food bags, beverage labels, and squeezable cosmetic tubes.

PET or Polyethylene Terephthalate is also known as polyester. This material is a very tough, heat-resistant plastic and has a higher melting point than BOP. You can find this type of material in clear soda and water bottles, electronic stickers, medical packaging, and oven-safe food trays. 

Both BOP and PET have low surface energy and are nonporous. Most flexographic printing applications require a surface energy of 38–42 dynes/cm to achieve stable ink adhesion. Corona pretreatment raises the dyne level of materials such as BOPP and PET into this optimal range, ensuring consistent wetting and print durability.

Corona Treatment In Printing: An Essential Process in Flexographic Printing

In flexographic printing, brands or companies often use nonporous materials in printing labels and packaging. Materials such as BOP or PET are used for stickers and small labels, which are naturally “slippery.” This makes it difficult for the ink or coating to adhere to the material. 

Corona treatment for printing solves this problem by increasing the dyne level and enhancing the surface energy. Let’s look at how corona pre-treatment can be beneficial in surface preparation:

1. Ensures Ink Adhesion – Corona pre-treatment increases surface energy. This prevents the ink from flaking or scratching, especially during shipping and handling.
2. Achieves Precise “Wetting” – A higher dyne level allows liquid ink to permeate and spread evenly across the film. This process is known as “wetting.” A higher dyne level helps eliminate flexo printing defects such as pinholing and bleeding. 
3. Enables High Speed Production – The corona pre-treatment allows processes to run smoothly and at maximum speed while maintaining consistent bond strength. This results in increased factory output. 
4. Addresses “Dyne Decay” Issues –  Since pre-treated substrates lose their effectiveness over time, pre-treatment refreshes the surface to ensure its peak receptiveness and adherence to flexo printing.
5. UV and Water-based Adherent – Corona treatment for printing enhances surface tension and supports environmentally-friendly ink. This leads to adherent bonds to PET and BOP synthetic materials.
6. Protects Brand Integrity – With longer-lasting packaging and product labels, end consumers can rely on the product information to stay visible on products for a very long time. You can be assured that relevant information, such as nutritional facts, expiration dates, barcodes, and branding, remains legible and visible over time. 

Minimizing Production Cost with Corona Pre-Treatment

Brands and companies often weigh the pros when deciding on “added services.” Corona pre-treatment is not an extra expense; rather, it is quality insurance. Corona treatment in printing is more beneficial than costly– here’s why:

1. Eliminates Costly Environmental Waste – Without high surface energy, your stickers, labels, and packaging could fail adhesion and labelling tests. Industries require proper labelling to keep consumers well-informed. Using corona treatment ensures that expensive substrates aren’t rejected due to ink flaking.
2. Prevent Batch Recalls – Product recalls happen when labels become faded when they reach the consumer. Ensuring a stable dyne level at the time of printing prevents your labels from fading. 
3. Reduces Flexo Printing Downtime – When the ink does not adhere properly to the substrates, operators often stop to adjust the ink chemistry or clean the flexo printing plates. The corona pre-treatment provides a stable dyne level, which leads to high surface energy. 
4. Lower Ink Consumption – When the substrates undergo proper “wetting,” the ink spreads more evenly and efficiently. Thus, the desired color density is achieved with a thinner, more consistent ink application. This saves money on consumables.

RAZP uses corona treatment in printing, which involves introducing ionized gases and applying voltage to the surface energy of a nonporous material. This treatment promotes bond formation between the substrates and materials, such as inks, additional coatings, or adhesives. Thus, this process reduces costly production waste. 

Conclusion 

Corona pretreatment is an essential process in flexographic printing, not an optional add-on.
By increasing surface energy and stabilizing the dyne level, it ensures reliable ink adhesion on non-porous substrates such as BOPP and PET, helping printed labels and packaging remain durable throughout handling and distribution.

Rather than being an added expense, corona pretreatment functions as a quality control step in the printing workflow. It reduces waste, minimizes rework and downtime, and improves ink efficiency by enabling consistent wetting and adhesion.

RAZP flexographic solutions integrate inline corona pretreatment to support stable surface activation and web handling during production. This allows manufacturers to achieve:

• Consistent adhesion and print quality across production runs
• Up to 18% lower ink consumption through even wetting and controlled surface energy
  

By integrating reliable corona pretreatment into the printing process, RAZP helps manufacturers deliver market-ready labels and packaging with confidence.