API Foils warns about the rise in corrosion cases

API Foils is encouraging customers to protect against the rise in corrosion on metallic foils. Over the past three years cases of corrosion on metallised labels and decorative packaging have increased significantly. 

API Foils believes this problem is easily overcome by providing foil blockers, printers and their customers with the correct specification information and greater awareness of some of the common causes.

Metallic foils can only be protected by the correct combination of substrates, coatings and materials used during processing due to the vulnerability of the aluminium layer within metallic foils. If the correct combination of materials and conditions are not met then any metallic foil will be susceptible to corrosion. 

Most corrosive reactions which may present themselves instantly or over a few days, weeks or even months, occur as a result of substances found on the substrate which react with the aluminium layer as a result of an insufficient protective adhesive layer. The effects of corrosion are easily visible due to the fine nature of the aluminium layer, creating cost and brand reputation implications.

Cases have been reported where the adhesive applied to labels has been too acidic or too alkaline, resulting in corrosion. This is often due to the cleaning regimes of gluing apparatus as opposed to the adhesive content. For example, the use of caustic soda and the residue it creates has been highlighted as a contaminating factor.

“Over the past few years we have seen instances of corrosion all over the world with about one case reported every two months yet for the 20 years preceding this, it was virtually unheard of,” explains international technical support specialist Andy Kerr.

“A possible cause for the increase in this problem could be a result of the global economic crisis. It would seem that the world recession has created a need for cheaper materials and less protective coatings and from this we have seen a proliferation of problems with corrosion.

“Here at API Foils we have to recognise that there has been ‘golden era’ with no cases of corrosion. We now have a great many customers who have never seen corrosion nor had any experience of it. We therefore have an important job to do in educating our customers and the end user to prevent this costly but fully avoidable type of damage and degradation.” API Foils uses the most stable grade of aluminium to limit the chance of corrosion but there are further steps that can be taken to prevent this costly problem including coating black inks and paper with a sealant or varnish prior to blocking; ensuring the substrate is not excessively wet; keeping the substrate free from salts; and using a pH neutral adhesive.