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Why Aren’t My Labels Sticking to Some Painted Metal Surfaces?

I’ve noticed that adhesion failures of labels using pressure sensitive adhesives (PSAs) to painted metal surfaces such as decorative street lamp posts or even some equipment cabinet panels is becoming more common.

The first suspect reasons might be application in low temperatures or a contaminated surface/poor surface cleaning.

But once these issues are ruled out, what else could be at play?

More frequently, manufacturers of commercial equipment are turning to powder coat paint processes vs traditional wet coat, solvent-based paints.

This is because power coat paints offer not only a tough, durable, attractive finish; but also can be cheaper, safer, and more environmentally safe to apply.

Powder coat paints can also present challenges for adhering the labels we may be required to apply to them, however.

What makes powder coat different from conventional paint?

Powder coating is applied as a dried paint in a powder form.

This is different than liquid paints that are dissolved in solvents that give off VOCs as they cure and dry and that can be dangerous to health and harmful to the environment.

With powder coating, the paint which is composed of very fine plastic particles is applied with a spray gun; which is similar in design to that used for wet paint coatings.

But the powder is attracted to the surface to be painted by induced, opposite electrostatic charges.

The powder coating is then ‘cured’ or bonded to the painted surface by baking at temperatures reaching several hundred degrees.

This produces a tough, chemically resistant, fused coating.

Why does powder coat make for poor adhesion of labels?

Where adhesion of labels comes into play, it’s important to remember that powder coat is a plastic material.

And many plastics are low surface energy (LSE) materials that the typical PSAs used on labels don’t stick well to.

In addition, finish texture of powder coats can be problematic. While some powder coat paints can produce a very smooth and high gloss finish, others and particularly thin powder coats can produce a textured or ‘orange peel’ like finish.

High gloss finishes can affect adhesion because they can be very slick, not providing much ‘tooth’ for adhesion.

But textured surfaces can provide an even greater challenge because the typically thin adhesive coating on labels is not thick enough to flow out and fill the micro-textured valleys of the surface; only contacting the high ‘peaks’ and making less than full or maximized contact with the surface.

Powder Coat Orange Peel Texture_Zoom
In addition to being ‘slippery’, some powder coat paints can have a textured or “orange peel” like finish. The surface of this example also has contours that some label materials conform poorly to. These properties can lessen contact surface and make adhesion of typical labels poor.

Contoured surfaces

Aside from a powder coat finish and apart from properties such as low surface energy and texture, some surfaces have contours that affect adhesion.

This is because some label materials are not flexible or stretchy enough to conform; especially to surfaces having compound contours such as that pictured above.

Options to overcome these challenges

Low surface energy (LSE)

Special adhesives are available that are engineered to stick to LSE surfaces.

Unfortunately, these adhesives are difficult, if not impossible to source on labels made from standard material offerings.

And the cost would become an issue for any label manufacturer sourcing a custom coated specialty adhesive label material due to low-volume sales usage and a minimum order quantity of material stock.

Fortunately, these LSE adhesives are available as laminating transfer adhesives in roll form and as a product not already coated to a label stock.

But they must be applied to a label stock by the label manufacturer as a separate process; which adds manufacturing cost and may present compatibility problems with some label materials.

Textured surfaces

Types of laminating transfer adhesives similar in form to those mentioned for LSE applications are available in thicker coat weights than the typical adhesive coating thickness on standard label materials.

These thicker coatings provide the ability for the adhesive to flow and fill the micro-textured valleys of the textured surface; thus maximizing contact area and therefore adhesion.

Again, these adhesives add complexity and cost to the manufacturing process.

Contoured surfaces

As noted, some common but high-quality label materials such as polyester are not at all conformable.

For contoured surfaces, there are readily available, high-quality vinyl label materials that exhibit the ability to stretch and provide high conformability to these curves.

Electromark

Some of Electromark’s standard label materials such as polyester or Duracryl® utilize an adhesive that is engineered to provide excellent adhesion on many LSE surfaces and powder coated paints, as long as they are smooth and not textured.

But for more challenging powder coat finished surfaces, Electromark also has high-quality conformable vinyl label materials, and specialty thicker laminating transfer adhesive options including LSE adhesives.

The key is providing full details of the surface your label will be adhered to so that we may determine and advise the best option to meet the requirements of your application.

Visit the Electromark website to learn more about the Electromark Advantage Follow us on Linkedin for new information and updates: Electromark Company

Brandon Furber View All

I have been in my present role as Technical Sales and Application Engineer with Electromark for 9+ years, and with the company for 14 years. My earlier experience with the company was with our printing and other manufacturing operations. My knowledge with Electromark and the industries it serves includes materials, products, process capabilities, weathering durability, regulations, and standards. See my Linkedin profile at https://www.linkedin.com/in/brandon-furber-0036644a/

With over 40 years of experience, Electromark specializes in identification and safety marking solutions for the electrical utility industry, other service utilities, and the outdoor industrial workplace. Our products are engineered for the harsh, outdoor environment.

2 thoughts on “Why Aren’t My Labels Sticking to Some Painted Metal Surfaces? Leave a comment

  1. Great blog Brandon, appreciate the insight and education on these specifics. Thank you for doing this. Great resource as well.

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