Influence of a Rhamnolipid Biocomplex on the Corrosion of Duralumin in the Case of Mechanical Activation of its Surface

The problem of inhibition of the corrosion of D16T aluminum alloy by surface-active products obtained as a result of the biosynthesis of Pseudomonas sp. PS-17 strain (rhamnolipid biocomplex) is studied by using the electrochemical and quantum-chemical methods. It is shown that the rhamnolipid biocomplex is capable of the efficient inhibition of the corrosion of D16T aluminum alloy in a synthetic acid rain. The efficiency of inhibition increases with the concentration of biosurfactant. As the critical concentration of micelle formation is attained, a subsequent increase in the amount of biosurfactant in corrosive media does not lead to any noticeable intensification of its protective (anticorrosion) effect. The mechanism of corrosion inhibition is connected with the adsorption of biosurfactant molecules on the surface of aluminum alloy with the creation of barrier films and the formation of difficultly soluble complex compounds on the anodic sections of the metal as a result of the interaction of rhamnolipid with aluminum ions. The rhamnolipid biocomplex efficiently prevents the corrosion of aluminum alloy in the case of its mechanical activation. The biosurfactants added to the corrosive medium increase the rate of recovery of protective films on the aluminum alloy in the stage of repassivation by a factor of 2–4, as compared with the uninhibited medium.