Application of Pseudomonas cepacia CCT 6659 Biosurfactant as a Metal Corrosion Inhibitor in a Constructed Accelerated Corrosion Chamber (ACC)

Corrosion is the deterioration of metals due to environmental exposure. Commercial inhibitors used to control corrosion often contain heavy metal salts, which are highly toxic to both the environment and human health. A biosurfactant produced by the bacterium Pseudomonas cepacia CCT 6659 was tested as a corrosion inhibitor on carbon steel and galvanized iron surfaces. Matrices based on plant ingredients with different compositions were tested in a laboratory-constructed accelerated corrosion chamber (ACC) simulating a critical maritime atmosphere in conditions of 40 °C, 5% NaCl, and 100% humidity. The most stable matrix was selected for biosurfactant incorporation in different concentrations, expressed as critical micellar concentration (CMC), and was applied to metal surfaces to evaluate its ability to inhibit corrosion. Additionally, to evaluate the potential of the biosurfactant as a low-toxicity corrosion inhibitor additive in paint systems, iron and carbon steel samples were coated with three biosurfactant-containing commercial paints and subjected to critical atmospheric conditions for testing coating effectiveness. The formulation containing vegetable resin as a plasticizer, oleic acid, ethanol, and CaCO3 was chosen to incorporate the biosurfactant. The addition of the biosurfactant at twice its CMC led to a reduction in carbon steel sample mass loss from 123.6 to 82.2 g/m2, while in the galvanized iron plates, the mass loss decreased from 285.9 to 226.7 g/m2 at the same biosurfactant concentration. When supplemented with the biosurfactant, the alkyd resin-based paint (A) ensured less mass loss in samples (46.0 g/m2) compared to the control without biosurfactant (58.0 g/m2). Using the paint formulated with oil-based resin (B), the mass loss decreased from 53.0 to 24.1 g/m2, while with that based on petroleum derivatives (C), it decreased from 82.2 to 27.6 g/m2. These results confirm the feasibility of using biosurfactants in biodegradable coatings, reducing the need for commercial corrosion inhibitors.