Why Ink Still Peels After Corona Treatment: A Practical Troubleshooting Guide

1. Separate Wetting Performance from Final Ink Adhesion

Wetting concerns how a liquid spreads on a surface. Adhesion concerns how the resulting ink layer remains attached after printing and the required drying or curing process. These are related, but they are not the same measurement.

Enercon's technical guidance explicitly states that dyne level does not guarantee adhesion. It identifies coating compatibility, material characteristics and process variables among the factors that affect the final result. Read Enercon's explanation of dyne level and adhesion.

Ask the ink supplier for the recommended substrate preparation and acceptance test for the specific ink. Avoid adopting one dyne target for every film, ink family and application simply because it worked on an earlier job.

Record what actually fails. Ink separating from the film, one printed layer separating from another and a soft ink layer rubbing away are different observations. Keep failed samples and photographs so the discussion is based on evidence rather than the general description "poor adhesion."

2. Check the Dyne Test Before Trusting the Number

A dyne result is useful only when the test is performed consistently. Record the test fluid or pen, its condition, the application method, the observation rule and the exact surface tested. Follow the test-product instructions rather than mixing procedures from different tools.

Enercon notes that dyne pens can become contaminated through contact with surfaces. A convenient production check should therefore not be treated as an infallible, highly precise measurement.

Compare samples from the untreated web, immediately after treatment and near the printing point where practical. Identify the intended print side clearly. A result from the wrong face, a different roll or an earlier production period cannot establish the condition of the surface currently receiving ink.

Also assess positions across the web. If the failure appears as a stripe or is concentrated near an edge, one reading from the centre may miss the relevant difference. Keep the location of each test associated with the corresponding printed sample.

3. Review Film Condition, Additives and Storage History

"The same film" is not a complete material specification. Record the supplier, grade, thickness, batch, treatment history and any declared slip or other surface-relevant additives. When a previously stable job changes, compare the incoming material records before assuming the machine has lost performance.

Vetaphone explains that material composition and additives affect treatment response, and that slip-agent migration and storage conditions can influence treatment decay. The practical implication is to assess the surface when it is used, rather than relying only on a treatment value recorded earlier. See Vetaphone's material and treatment-durability guidance.

Review the web path for handling and contamination opportunities. Keep this investigation specific: identify where a surface contacts equipment, how rolls are stored and whether cleaning or handling practices changed.

If contamination is suspected, agree on a controlled comparison with the film and ink suppliers. Do not introduce an unapproved cleaner or primer during the test and then attribute the entire improvement to corona treatment.

4. Calculate Treatment Dose at the Actual Production Speed

Generator output alone does not describe how much treatment is applied to a moving surface. Width, line speed and the arrangement of treated sides also matter. Enercon's watt-density calculator expresses this relationship using power, electrode width, speed and the number of treated sides. View the original calculator and formula.

Consider a hypothetical single-sided process using 3,000 W across an active width of 0.5 m. The table below illustrates how changing speed affects the calculation.

These are hypothetical calculations, not recommended process settings or a Hefeng performance test. The example does not establish that 60 W·min/m² is suitable for a particular film or that the installed equipment can deliver the proposed condition.

Use the same units throughout. For two-sided or independently powered stations, confirm the allocation of power and active width for each treatment path instead of applying a side-count adjustment without checking the actual arrangement.

Restoring the calculated dose does not guarantee identical adhesion. Verify the resulting surface condition and printed sample. A generator's maximum rated output is not a substitute for the recorded output used during the trial.

5. Check Ink Compatibility, Drying and Curing in Parallel

Corona treatment cannot establish compatibility between every ink and every substrate. Confirm the ink series, film grade, additives and any primer requirements with the ink supplier. Record whether the formulation or ink-handling procedure changed when the problem appeared.

Sun Chemical's flexographic adhesion troubleshooting guide identifies unsuitable ink selection, inadequate drying and other printing variables alongside substrate treatment. Its energy-curable guidance separately identifies inadequate exposure, contamination and excessive press speed as possible curing issues.

This is especially important when a failure begins after a speed increase. The change may reduce corona treatment dose and alter drying or curing conditions at the same time. Do not attribute the result to one system before reviewing both.

Use the ink supplier's specified conditioning and test timing. A fresh print tested immediately may not be comparable with a sample evaluated later. Document ink film, drying or curing settings and the delay before testing.

Technical references: Sun Chemical adhesion troubleshooting and energy-curable ink curing guidance. Apply recommendations through the technical support for the actual ink system.

6. Use the Failure Pattern to Organise the Investigation

A failure pattern helps select the next comparison; it does not prove the root cause by itself. Use the observations below to build a short, controlled trial rather than changing several settings at once.

For equipment checks, record the station identification and request review of electrode condition, alignment, dielectric condition and other relevant items under the manufacturer's service procedures. A recipe change cannot correct every mechanical or maintenance issue.

Keep untreated, treated and printed samples clearly labelled. Use a controlled comparison with one planned variable at a time where practical, then retain the result and operating conditions.

7. Match the Corona Station to the Printing Process

Hefeng's Narrow Web Coronastation page publishes the following reference configuration for label and narrow-web printing applications.

These are supplier-published product options, not a guarantee that every combination delivers the required treatment on every substrate. Confirm the offered station, generator, operating envelope and sample-test result together.

For a new installation or retrofit, provide the film type, thickness, width, operating-speed range and the surface receiving ink. Include the existing web path, available space and machine interfaces. The treatment station and generator should be specified as a compatible system.