The objective of the project was to research and develop a formulation of new antimicrobial nanostructured durable coatings chemically grafted onto non nutrient chromate free primer of fuel tanks. The strategy to formulate these new antifouling coatings specifically designed to inhibit the adhesion of microorganisms were based on two aspects that will take place simultaneously: physiochemical incompatibility between the surface of the coating and microorganisms and sub-products generated by them, and biochemical elimination of microorganisms to inhibit their adhesion to the surface of fuel tanks by a synergistic combination of inorganic and/or organic biocides embedded in the coating, including nanomaterials and micro- or nano-encapsulated chemicals.
Surface morphology (SEM, AFM), surface chemistry (XPS), surface tension (contact angle), adhesion and durability of the new antifungal coating was evaluated. The effect of growth inhibition for specific microorganisms present in aircraft fuel was measured according to microbiological analysis and studies of formation, adhesion and elimination of biofilms onto the new developed antifouling surfaces. The new antifungal coating formulations was compatible with fuel and will not affect fuel combustion. A special interest was addressed to potential nano-safety and nano-toxicity issues.
Microbial growth in aircraft fuel tanks is one of the main sources of contamination of aircraft fuel, plugging of flow of fluids systems and, particularly microbially influenced corrosion of fuel tanks.
Microorganisms from aircraft fuel need water to growth and this water come form the intrinsically fuel moisture content and additionally water from atmospheric moisture condenses in the wall of fuel tanks. Among different microorganism Hormoconis resinae (also known as the “kerosene fungus”) and Pseudomonas aeruginosa are the most prevalent.
The current main methods to control the microorganisms’ growth in aircraft fuel are based on maintenance, periodical removal of water from fuel tanks, and treatment, addition of additives as fuel preservatives.
These methods are not enough to solve the problem and there is an urgent need to develop better methods to control the microbial contamination.
In that sense the AMICOAT project proposed to develop new antimicrobial coatings to apply onto fuel tank walls. The antimicrobial coatings conferred antibioadhesion properties to the fuel tanks walls and they allowed the controlled release of biocides from the fuel tank walls to the water/fuel interphase.
The aim of AMICOAT project was to develop two different coating systems, a polymeric nanocomposite antimicrobial coating and a silica sol-gel antimicrobial coating. The main characteristics of the two new coating systems were:
- good adhesion with epoxy primer due to the grafting strategy and,
- durable antimicrobial properties due to the encapsulation of biocides, that will be incorporated in the two both polymeric and inorganic-organic coating systems.