Inventors from Texas A&M University in the US claim that a hygienic coating on galvanised steel food storage containers reduces the risk of corrosion by 70% – creating a bacteria-repellent surface.
Grain silos are an example of galvanized steel used for food storage © Fabio Alcini/Shutterstock
The coating is made from silica nanoparticles immobilized on the steel surface and modified with a layer of trichloro(1H,1H,2H,2H-heptadecafluorodecyl)silane (THFS), a low surface energy organosilane. It has been.
It has been shown to reduce bacterial strains over a seven-day period, reducing the adhesion of the food poisoning bacteria Aspergillus.
The research group took inspiration from lotus leaves, which powerfully repel water droplets. The university's Dr Mustafa Akhbult said they were able to apply this design characteristic to surface texture and chemical reactions to similarly improve galvanized steel.
“Superhydrophobicity and anti-fouling properties work together to make it difficult for bacteria to adhere to a surface. Superhydrophobicity creates Cassie-Baxter states with trapped air pockets, minimizing contact between the bacteria and the surface. Nanoscale roughness also reduces the contact area available for bacteria to attach,” Akbulut points out.
The coating is applied in a two-step process. First, the steel is immersed in a silica nanoparticle suspension for 24 hours, dried, and sintered at 630 °C for 2 hours to immobilize the particles. The silica-coated steel is then soaked in a THFS solution for 24 hours to chemisorb the organosilane layer onto the surface.
The research team measured the superhydrophobicity of the coating using contact angle goniometry and showed that the static water contact angle was 157 ± 3.6°. Its antifouling properties have been determined by various assays such as mud coverage test, fungal growth observation, bacterial adhesion quantification using scanning electron microscopy, and agar plating.
Electrochemical characterization, especially linear sweep voltammetry and Tafel analysis, have been used to find corrosion reduction. They found that in the presence of Salmonella enterica the corrosion rate decreased from 0.00116 ± 0.00013 mm/year for bare steel to 0.00046 ± 0.00017 mm/year for painted steel.
The researchers envision their coating being used to manufacture grain silos and other food-related storage units and containers, and believe it could also benefit a range of food engineering processes and agricultural fields by reducing mud contamination.
They report using a similar approach, albeit at different temperatures, on a variety of surfaces including aluminum and plastics such as high-density polyethylene and PVC.
Akbulut points out that the study did not involve toxicity testing or safety assessment for human exposure. Determining whether the coating is safe for human contact will require additional research to focus on potential health effects and ensure compliance with relevant regulations regarding food contact materials. .
Author Alex Brinded
