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New Coatings Inhibit Corrosion, Biofilms

Friday, April 15, 2016

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A Saarbrucken, Germany-based research center is working on coatings advancements intended to benefit anticorrosion and antifouling applications.

INM – Leibniz Institute for New Materials announced its developments of a special type of flake-like zinc-phosphate nanoparticles, as well as new nanocoatings that reduce microbes and persistent biofilms on heat exchangers, in statements released Wednesday (April 13).

The special type of flake-like zinc-phosphate nanoparticles developed by research scientists at INM are constructed in a way that slows down the penetration of gas molecules into the metal.

Additionally, INM is introducing new nanocoatings that reduce microbes and persistent biofilms on heat exchangers. When coated with these paints, heat exchangers require intensive cleaning far less often, the scientists said.

Increasing the Gas Barrier for Corrosion Protection

Steel is used in architecture, bridge construction and shipbuilding to extend the longevity of these kinds of structures. The material must not lose any of its strength and safety properties during its many years in service. With this in mind, the steel plates and girders require extensive and durable protection against corrosion—particularly against attack by oxygen in the air, water vapor and salts, INM explained.

INM nanpoparticles to prevent corrosion
INM – Leibniz Institute for New Materials
 

Current techniques to prevent corrosive substances from penetrating into the material include creating an anti-corrosion coating by applying layers of zinc-phosphate.

Now, INM’s research scientists have developed a special type of zinc-phosphate nanoparticles. Unlike conventional, spheroidal zinc-phosphate nanoparticles, the new nanoparticles are described as “flake-like” and are 10 times as long as they are thick. These properties are said to slow down the penetration of gas molecules into the metal, according to INM.

“In first test coatings, we were able to demonstrate that the flake-type nanoparticles are deposited in layers on top of each other thus creating a wall-like structure,” explained Carsten Becker-Willinger, head of Nanomers at INM.

“This means that the penetration of gas molecules through the protective coating is longer because they have to find their way through the ‘cracks in the wall.’”

The result, he said, was that the corrosion process was much slower than with coatings with spheroidal nanoparticles where the gas molecules can find their way through the protective coating to the metal much more quickly.

Additional tests validated the effectiveness of the new nanoparticles, the scientists said. Here, they immersed steel plates both in electrolyte solutions with spheroidal zinc-phosphate nanoparticles and with flake-type zinc-phosphate nanoparticles in each case.

After just half a day, the steel plates in the electrolytes with spheroidal nanoparticles were showing signs of corrosion, whereas the steel plates in the electrolytes with flake-type nanoparticles were still in perfect condition and shining, even after three days.

The researchers said they created their particles using standard, commercially available zinc salts, phosphoric acid and an organic acid as a complexing agent. The more complexing agent they added, the more anisotropic the nanoparticles became, they added.

Antifouling Treatment for Heat Exchangers

INM researchers also looked at the accumulation of persistent biofilms or sticky residues in heat exchangers, particularly in the food industry, which requires high standards of hygiene. In applications like these, heat exchangers require cleaning at regular intervals using aggressive chemicals.

While research focused on food industry uses, the paint developed could also be used in other contexts, Becker-Willinger said, including cleaning wastewater in water purification plants, for example, to prevent biofilm from accumulating on filters or tubes.

cleaning filter
© iStock.com / DenGuy
 

To address these issues, the institute has introduced new nanocoatings that reduce the effort required for cleaning heat exchangers. For these new coatings, the scientists combined anti-adhesive and antimicrobial qualities; heat exchangers coated with these paints require intensive cleaning far less often, the research team said.

To prevent microbes, bacteria or fungus from adhering to surfaces, the scientists used colloidal copper in the coating. Due to the oxygen or water that is present in many foodstuff processes, for instance, copper ions are created from the copper and  travel to the surface; as a result of their antimicrobial effect, they prevent microbes from settling there, the team said.

The developers achieved the anti-adhesive characteristics by introducing hydrophobic compounds that are similar to common Teflon, they said. These prohibit the formation of any undesired biofilm and allow residues to be transported out more easily before they clog up the channels of the heat exchangers.

“In addition, we can keep the paint chemically stable. Otherwise, it would not withstand the aggressive chemicals that are required for cleaning,” explained Becker-Willinger.

Adding that the paint could also be adapted for special mechanical loads, he explained that this was important for paint used in heat exchangers, too. Due to mechanical vibrations, the individual plates of the heat exchangers could be subjected to a certain amount of abrasion at points of contact.

The paint can be applied using standard methods such as spraying or immersion and subsequent hardening, INM said. It can be used on stainless steel, alloys, titanium or aluminum, it added.

By selectively adapting individual constituents, the developers said they will be able to respond to the particular, special requirements of interested users.

About INM

According to its website, INM conducts research and development to create new materials for today, tomorrow and beyond. Chemists, physicists, biologists, materials scientists and engineers team up to focus on these essential questions: Which material properties are new, how can they be investigated and how can they be tailored for industrial applications in the future?

Four research focuses determine the current developments at INM: New materials for energy application, new concepts for medical surfaces, new surface materials for tribological systems and nano safety and nano bio. Research at INM is performed in three fields: nanocomposite technology, interface materials, and bio interfaces.

It is an institute of the Leibniz Association and has about 220 employees.

The developers will be demonstrating their results for both of these discoveries and the possibilities they offer at the Hanover Trade Fair as part of the Research & Technology trade show, April 25-29.

   

Tagged categories: Antifoulants; Asia Pacific; Bridges; Coating chemistry; Coating Materials; Coatings Technology; Corrosion protection; Corrosion resistance; EMEA (Europe, Middle East and Africa); Foul release; Latin America; Nano and hybrid coatings; Nanotechnology; North America; Protective Coatings; Research and development; Shipyards; Wastewater Plants; Zinc Phosphate

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