News Release

Challenge surface coating technology to solve your processing problems

18th May 2004

 
Colin John, managing director of surface coating specialist Poeton Industries, suggests that coating technology can solve many processing problems and save time, money and disappointment.

Surface coatings can be designed-in as part of a product's performance, used to coat the surfaces of the machines or moulds used in its manufacture, or applied after manufacture to protect its surfaces, further enhance its performance or improve its appearance.

A surface coating can be as simple as a coat of paint (an 'envelope' coating), as common as galvanising (a 'sacrificial' coating) or as complex as a zinc composite with a two-pack epoxy polymer finish (a combination of both).

Depending on the environment the first may last a couple of months or a couple of years, while the last could still look as good as new after twenty years, even in an aggressive atmosphere.

To quote an example, our research shows that the effect of corrosion and wear occurring together can cause more than ten times the loss of material from a component than either one acting alone. The phenomenon is caused by the wearing away of normally passive layers that might otherwise slow the corrosive attack, which immediately exposes the substrate to fresh corrosion. Which is why, to get the best from a surface coating, it needs to be carefully specified to ensure it is 'fit for purpose'.
The latest developments in surface coatings have the potential to make processes more efficient, lower manufacturing costs, improve product performance and control quality - provided manufacturing companies talk to a coating specialist.

Tapping into the experience of specialist surface engineering companies at the earliest stage of a product or process means involving them in component design, materials and coating selection, and processing and production. An understanding of the customer's requirements will help them decide on the most suitable coating from a range that includes nickel and nickel composites, hard chrome, hard anodising, thermal spraying and numerous other specialised composite coatings.

Coatings can be applied to a wide range of base materials and complex shapes, making them suitable for many applications, including those requiring USDA and FDA compliance, extremes of temperature from -200ºC to +285ºC or chemical resistant properties.

Moulding processes are typical areas where problems solved by surface coatings have achieved significant success. In most there is a need for some form of mould release to speed up production, maintain product quality and reduce or eliminate costly mould stripping and cleaning time.

The traditional solution, an aerosol spray release agent manually applied by a machine operator, may appear to be the easy option but can have serious cost and environmental implications when examined closely. Application of the spray can be difficult to control and coverage difficult to measure accurately. The coating may be uneven, leading to patchy product release, and over-spray is wasteful and potentially harmful to operators. Even automated spray equipment raises environmental concerns with spray particles in the atmosphere. Legislation also makes disposal of empty cans a costly problem.

However, replacing conventional spray release agents with a specialised coating provides considerable cost and operational benefits. Carry-over of release agent onto the product is eliminated, the high cost of release agents and disposal of aerosols is greatly reduced, and as most moulds can be stripped and re-coated, their working life can be extended significantly.

We recently applied such a coating to solve a very sticky packaging problem for Rexam, one of the world's top-ten consumer packaging suppliers and a leading European supplier of thin wall plastic containers for the food industry.

The company developed a proprietary process to mould high volume trays using PET, an advanced packaging material that is specified by major food brands because its clear finish allows consumers to see the product inside the pack.

However, whilst PET has obvious advantages it can be difficult to process in high volume moulding machines, being both abrasive and sticky. Its abrasive properties caused aluminium moulds to wear quickly and its stickiness made it difficult to remove trays from moulds - problems that had a seriously affect on high volume production. Also, because trays stick together when stacked, de-nesting was difficult and slowed down the customer's production lines. Both problems were experienced on a line producing trays for a major food product line.

To overcome the de-nesting problem Rexam had been grit blasting the mould to roughen the surface, and blending an expensive migrating wax additive with the PET. Whilst this approach improved de-nesting it didn't solve the mould wear problem and, as the additive left a residue, the mould also needed regular cleaning.

We developed a self-lubricating nickel alloy composite coating to reduce wear in the mould cavity and also suggested bead blasting rather than grit blasting as a more effective pre-treatment for use with this coating.

After six weeks continuous testing on a 120-cavity drum mould with only twenty cavities coated, there were no signs of wear in the coated cavities and Rexam were sufficiently impressed to have the whole tool coated. But the real surprise came when trials with only half the amount of the expensive de-nesting additive showed a significant improvement and reduced additive costs.

The process now produces 1.5 million of the twin-cavity trays each week to feed a production line that is operating every day of the week.
A similar coating solved another mould processing problem when it was used to 're-cover' a set of rusty filter moulds, saving South Wales based Sogefi Filtration over £25,000!

To produce an after-market air filter the manufacturer of air, oil and fuel filters for cars and heavy goods vehicles was using 150 sets of feretic stainless steel moulds supplied by a sister company. Prior to production the moulds were coated with a PVC chemical incorporating a release agent, which then had to be oven cured.

Despite the coating, the presence of carbon in the stainless steel caused the moulds to corrode, making it impossible to remove filters without ripping their seals.

A zinc coating applied by a local company also failed to prevent sticking; and even getting coatings to stick to the moulds was proving to be a problem.

Faced with a £25,000 bill to replace the moulds, which by this time were very badly rusted and difficult to clean or polish, we were asked to advise. We suggested a nickel polymer coating we had developed for rubber and polymer moulding applications. Its combination of permanent lubricity and high hardness enabled filters to be easily released and significantly extended the life of the moulds.

Eighteen months and an estimated 60,.000 filters later, there are no signs of wear or deterioration in the coating, even though a metal gauze inside the filters rubs against its surface during the process.

While on the subject of moulds, a cost-efficient option to replace expensive alloy moulds is to manufacture from low carbon steel and coat them. A correctly specified coating can ensure that performance is maintained, even improved, and costs are further reduced because moulds can be machined from more workable and readily available metals.

Coatings can also be designed to meet the most stringent environmental needs of customers and many coating companies have invested considerable resources in environmentally friendly coatings and processes.

The new Keronite coatings for example - described by the industry as a quantum leap in coatings for aluminium and magnesium - use a completely non-toxic and environmentally friendly wet chemistry, where traditionally the majority of anti-corrosion coatings have been based around toxic and/or environmentally unfriendly wet chemistry processes.

The latest high-velocity thermal spray technology also produces environmentally friendly coatings using a dry, non-toxic chemistry. The tough, flexible coatings produced have excellent wear, non-stick and release properties that can solve all the 'sticky substance' problems encountered in areas such as adhesive formulation, label printing, tape manufacture or converting. It is an ideal release system for metal parts that are in contact with adhesives, where it can eliminate downtime and cleaning delays.

Sticky substances are a major cause of processing problems, both for machinery manufacturers and operators and it is an area where much research has been done by coating specialists. To demonstrate confidence in our Apticote coatings, we have thrown down the gauntlet to the processing industry with an offer to test materials against our range. We are so convinced that coating the contact surfaces of tooling, moulds or machine rollers will solve 'Sticky Substance' problems, that we are offering to coat sample parts free of charge and test them against problem materials.

The challenge should be irresistible to companies involved in adhesive formulation and tape manufacture, printing and packaging, and food, cosmetics and pharmaceutical processing.

With so much innovation available in surface coating technology, manufacturers should take the time to ask for technical advice and discuss sample part processing. It can save money, time and a considerable amount of stress!

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File: Process Products