For many years, RUBIG has ranked among the global market leaders in the field of coating systems. Our primary focus in system and process development is on plasma-activated chemical vapour deposition (PACVD). Starting in 2013, our in-house R&D intensified its research activities in the field of functional coating with antimicrobial materials. Several FFG [Austrian Research Promotion Agency] projects in cooperation with external research partners have enabled the company to gain valuable know-how about coating a wide variety of metal and plastic substrate materials, and about their particular environmental impact.
Dipl. Ing. Dr. (mont) Christian Dipolt, MBA
Schafwiesenstr. 56, 4600 Wels, AUSTRIA
Phone: +43 (0) 7242 / 66060
The aim of this development work is to reduce the risk or to completely prevent infections via smear and droplet infections. One focal point is nosocomial infections, i.e. infections with antibiotic-resistant bacteria. The focus is also shifting to areas where continuous hygiene and disinfection measures cannot be guaranteed. The European Center of Diseases Control estimates that more than 4 million patients contract nosocomial infections each year, making it one of the most common complications of hospitalisation. However, non-resistant bacteria and viruses are also found on many surfaces and, in the event of infection, not only have health consequences for the affected individual, but also cause enormous damage to the national economy. Biocidal surface treatment prevents the settlement or survival of viruses and bacteria on a variety of different substrates, helping to break the chain of infection.
The importance of copper as a biocide has been known for a long time. Today, the mechanism of action and the effectiveness of copper on bacteria have already been widely researched and described in detail in the literature. However, while the same is true for the effectiveness of copper on viruses, we know less about the specific processes and interactions that underlie the antiviral effect. In general, copper is extremely harmful to microorganisms, i.e. bacteria and viruses alike, even in small doses. Redox reactions (reduction-oxidation reactions) cause an exchange of electrons. Positively charged copper ions are formed, which lead to the formation of free radicals. These break down the outer membrane and subsequently the DNA of the bacterial and viral cells. This process not only destroys the organism, it also leads to corrosion of the copper surface.
Copper is generally characterised by a strong tendency to corrosion. Depending on the surrounding atmosphere, various corrosion products are formed, some with a high degree of adhesion to the surface. As with the destruction of bacterial cell material, electrochemical corrosion reactions lead to redox reactions - i.e. an exchange of electrons. The high conductivity of copper results in a spatial separation between reduction and oxidation. The oxidising agents are usually neutral and alkaline media such as oxygen, or acidic media such as protonated water molecules (H3O+). They trigger the reaction and initiate the dissolution of the metal as a result of oxidation. This results in holes, depressions, grooves or porous metal areas. The corrosion process is considerably influenced and accelerated by mechanical stress, e.g. stress corrosion cracking, and contamination by micro-organisms or similar.
Copper alloys are a well-established option for slowing down the corrosion process.
Copper-aluminium or copper-aluminium-zinc and copper-titanium alloys have already been successfully tested. They are widely used in industry, for example in aircraft construction (AlCu) or as a material for electronic components (CuTi). RUBIG is researching further alloy systems in-house using the results already obtained from theory and practice as a basis. The highest priority is undoubtedly to maintain the biocidal effect. At the same time, we are trying to increase the service life of the copper coatings.
A longer component life of coated components is determined on the one hand by the adhesion of the coating itself and its loading with biocidal active ingredient or its release rate. But, on the other hand, it is also defined in terms of the possibility of recoating after specified service life and removal (coating removal) of the "old" layer. Copper coating layers can be removed by abrasive cleaning, chemical etching, electro-cleaning or reactive cleaning.
RUBIG has already established a wide variety of carbon and titanium-based coating processes in the industry with the objective of maximising resistance to wear and corrosion. In the field of medical technology, RUBIG faced requirements such as the biocompatibility of ceramic implants and antiviral surfaces. A PVD (Physical Vapour Deposition) coating to specifically kill bacteria and viruses on surfaces was developed several years ago in the course of a COIN (COoperation & INnovation) project together with the Wels University of Applied Sciences.
At that time, such surface technologies were not yet accepted. In the wake of the pandemic, the role of surfaces in the spread of bacteria and viruses has once again come into focus, triggering a renewed focus on the topic under the title "RUBIG AntiViralCoating". The aim is to apply a copper/copper oxide coating to surfaces that are exposed to increased contamination, for example in highly frequented public places, in order to reduce or completely prevent the spread of viruses and bacteria. Components made of metal, plastic or filter materials, themselves consisting of non-woven materials or foam, can be coated.
The antimicrobial and antiviral effect is generated by the oxidation of the surface. Tests with human coronaviruses (HuCoV-229-E) show that there is a significant drop in infectious species after only 10 minutes of contact. If the chemical composition of the coating is appropriate, the number of infectious species will have fallen below the detection limit after 20 minutes. Properties such as durability, effectiveness and haptics can be influenced by the targeted addition of chemical elements to the coating. The type of coating can be customised to the specific requirements of the customer and the coating system is also constantly being developed.
External research partners such as the University of Applied Sciences in Wels and Joanneum Research in Niklasdorf/Styria with their experience in the field of antiviral coatings and PVD technology are participating in the project. RUBIG is also supported by Med Uni Graz, which carries out tests on the effect of the surfaces against viruses and bacteria together with the Hygiene Institute. PVD technology is a strategic addition to the surface competence for RUBIG system and hardening technology. The PVD system and process technology we have developed in-house complements the product portfolio of RUBIG Industrial Furnaces as an additional, future mainstay.