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Novel aluminium surface treatment achieves corrosion resistance of stainless steel

01 April 2015

Krijn Verwijs processes shellfish products. At its Yerseke, Netherlands facility, the company has long battled with the effects of corrosion due to the seawater-infused atmosphere at the plant. For the conveyor drives, however, they seem to have found a solution to this problem.

Fresh catches arriving at the factory are transferred into large holding basins with a constant flow of clean salt water to keep the product in good condition and to thoroughly rinse off sand and debris. Given the close proximity of these containers and the fact that live mussels are then conveyed wet, all processing lines throughout the factory are inevitably exposed to a humid, salty atmosphere.

These conditions lead to swift corrosion of all sorts of unprotected metal surfaces, including drives serving the numerous conveyor lines. For conventional cast iron geared motors, rust spots start appearing on new systems in a matter of weeks, and the expected life of such units is only a year or two.

Special coatings or varnishes merely help to delay the onset of corrosion, while stainless steel drives have not been considered since they are not only very costly, but also impractical due to their requisite disruptive cool-off periods before every hose-down. 

Frequent drive replacements were thus the order of the day for Krijn Verwijs until the company was made aware of a new approach to drives deployed in aggressive environments, namely Nord Drivesystems’ ‘Clean Drive’ nsd tupH surface treatment technology for aluminium cased geared motors. Claimed to achieve stainless steel grade resistance to corrosion, these surface treated aluminium geared motors are easily and effortlessly washed down.

While these aluminium geared motors do come at a premium compared with the price of conventional cast iron units, both lab trials and extensive real-life testing in the factory in Yerseke indicate that nsd tupH treated components will last for the better part of the typical ten-year lifetime of a conveyor line, or even outlast the line altogether. Krijn Verwijs has begun to roll out Clean Drive nsd tupH systems throughout its plant in order to tackle the hitherto high costs associated with the frequent replacement of drives and heavy maintenance schedule.

Conversion, not coating
Nord’s nsd tupH treatment is not the application of a coating, but rather a surface conversion that produces a base layer that is permanently bonded to the substrate. Applied via an electrolytic process, this treatment renders aluminium cases as resistant to corrosion as stainless steel. Moreover, the scratch resistant surface is more than six times as hard as untreated alloy, and a thousand times as hard as paint.

Featuring a very lightweight, compact, and self-draining design, Clean Drive nsd tupH systems for the food industry can be easily washed down. They are resistant to common chemical cleaning agents, and neither acid nor alkaline rinses or high-pressure cleaners will damage these treated surfaces. In addition, nsd tupH is universally available for all Nord aluminium gear unit and motor products – unlike many stainless steel geared motor ranges which manufacturers tend to limit to just a few types. 

The salty atmosphere everywhere in the Krijn Verwijs Yerseke production centre makes this seafood factory a textbook case for adverse environmental conditions – several hundred 1.5kW class geared motors in various conveyor lines have long suffered from rapid corrosion.

A full transition to resilient Clean Drive nsd tupH systems is now underway, and in the months and years to come, every drive at Krijn Verwijs will eventually be replaced by an extra-durable Nord geared motor, which the company expects to last at least five times longer than the original geared motors.

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