Clean and protect in one step

Published by: Mike Excell – Thu 14 Apr 2011
Feature Type: Additive manufacturing

Norpe is one of the most experienced manufacturers of commercial refrigeration in Europe. It began manufacturing in 1953, and today the company’s refrigeration technology can be found in supermarkets, petrol stations, cafes and snack bars across Europe. In the summer of 2009 at its Porvoo production site near Helsinki, the company switched from an iron phosphating procedure to a nanoceramic conversion process using Bonderite 40 CC.  This Henkel product combines cleaning and corrosion protection in a single step, and the change has delivered improvements in terms of economy and ecology as well as quality.

New coating technology put to practical test
“Anyone investing in a Norpe product expects a high-quality and durable refrigeration unit that still works impeccably even after 20 years,” says Pekka Silvennoinen, responsible for the painting process at Norpe. The quality of surface treatment is an important factor, because refrigeration systems are exposed in service to an elevated risk of corrosion due to high humidity, condensation and the use of aggressive cleaners. In its search for an improved pretreatment process offering greater corrosion protection paired with lower process costs, the company found that Bonderite 40 CC met its requirements.

The dropping test confirms the high adhesion of the cured powder coating on the conversion coatingOn the metal surface, the novel process generates a high-density nanoceramic conversion layer that gives long-term protection from corrosion creep and improves paint adhesion. Today, Bonderite CC 40 is utilised at Norpe as a cleaner coater in a 3-stage process including rinsing baths and final rinse. The multi-metal process enables the coating of different substrates on the same line. Surface degreasing and coating take place simultaneously in the first spraying zone of the pre-treatment tunnel with a contact time of 90 seconds. Some 250,000 m2 of metal are coated this way per year.

Tests confirm quality
Before its introduction on the spraying line, Bonderite CC 40 first underwent extensive laboratory tests. The results exceeded the expectations of Raimo Tyyskä, who works in Norpe’s R&D department: “We had salt spray tests carried out by Henkel and by an independent paint manufacturer in order to find out if the finished coating meets our high standards. The final evaluation showed that the quality of corrosion protection is appreciably better than that of the previously used iron phosphating method.”

For instance, in the salt spray test lasting 720 hours on steel, corrosion creep of only 1mm was measured. On aluminium, there was no evidence of corrosion even after 1,000 hours. The last practical test on the line also proceeded without a hitch. During the summer break, technicians from Norpe and Henkel cooperated closely in order to ensure a smooth switch-over to the new process. “Henkel helped us enormously by providing intensive on-site support during the first few weeks to tune the process to our exact requirements,” says Pekka Silvennoinen. After thorough cleaning of the installation, the Bonderite CC 40 process proved to be completely stable on the existing line, without needing any new engineering investment.

Resource-efficient production
Besides the improvement in surface quality, the fact that Bonderite CC 40 also overcomes other process shortcomings was a major factor in choosing the new method to optimise the coating line. Pekka Silvennoinen stresses the positive effect in both economic and ecological considerations. “Abandoning iron phosphating significantly reduces the burden on the environment. Compliant with the local regulations, Bonderite CC 40 avoids any phosphate issue in waste waters, and doesn’t generate toxic heavy metals or organic substances, which had to be disposed of at great effort and expense in the past.”

A year after implementation, Silvennoinen reports that the benefits of the new system on Norpe’s 6000 litre cleaner-coater tank are substantial. “We used to have to change this entire volume of water roughly three times a year in order to ensure stable iron phosphating. But thanks to its far lower conductivity, Bonderite CC 40 extends bath life considerably and reduces overall water consumption.” At the same time, the company no longer has to purchase the licence required for the use of phosphates in industrial processes in Finland. Equally positive on the financial side is that fact that maintenance work has been reduced to a minimum. “Since minimal phosphate sludge was generated at Norpe in the past year, there are no visible signs of contamination in the installation today,” Silvennoinen adds. Indeed, the line is now cleaned once per year for preventive reasons only.

Low energy consumption reduces operating costs
Norpe has also achieved substantial savings as regards energy consumption. Classical phosphating usually takes place at an operating temperature of 55°C. For Raimo Tyyskä, a reduction in the bath temperature by over 10 degrees Celsius is therefore another powerful argument for recommending Henkel’s process. “In times of slack business when the economy is weak, reducing operating costs is becoming a vital necessity for companies. With Bonderite CC 40, Norpe has managed to cut gas energy costs alone by about 30 percent.”

Based on the good results obtained in refrigeration equipment manufacture where the nanoceramic process has now been running smoothly for a year, Norpe will soon be switching the second production line over to the new technology. “Besides improving the quality of our products, we have been making considerable efforts over the past few years to make our production processes more sustainable. The new coating process from Henkel makes a key contribution to this,” concludes Raimo Tyyskä.

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