PEO coating containing copper: A promising anticorrosive and antifouling coating for seawater application of AA 7075

Metal products in seawater have to face two important phenomena: corrosion and fouling. Corrosion represents a serious issue that can eventually compromise the integrity of the product. Biofouling, defined as the colonization by organisms (bacteria, algae, plants, and animals) on wetted surfaces, is problematic because it increases weight and consequently fuel consumption in boats. Moreover, the two phenomena are mutually sharpening. PEO is a quite new surface treatment, which increases corrosion and wear resistance of light alloys much more than traditional anodizing, and allows the introduction of particles into the coating. In this work, the corrosion and antifouling properties in seawater of copper containing PEO coating, produced on AA 7075, were studied. PEO coatings were produced working at high current densities and in short treatment times, and the particles were incorporated into the coatings by simple addition to the electrolyte. PEO coatings were also used as possible substrate for commercial painting and untreated samples were tested as comparison. The obtained coatings were characterized by SEM-EDS, XRD, and potentiodynamic tests. Corrosion and antifouling properties were evaluated in situ through immersion of several samples in seawater for 4 weeks, intermediate collections and analyses each week with stereomicroscope and SEM observations. The results showed that the PEO coated samples containing copper powder exhibited antifouling effect. The use of PEO coating as substrate for painting can improve performance both against corrosion and fouling, in presence of defects or damages in the paint.