Annalisa Acquesta

The Effect of Graphene on the Protective Properties of Water-Based Epoxy Coatings on Al2024-T3

0.5 and 1% wt. of graphene nanoflakes were added to an anticorrosive additives-free water-based epoxy resin applied to Al2024-T3 samples. Calorimetric (DSC) and adhesion (cross-cut test) tests indicated that the presence of graphene did not affect the polymerization process of the resin or its adhesion to the substrate while it had some effect on its wettability. Electrochemical Impedance Spectroscopy (EIS) results obtained suggested that the addition of a small amount of graphene greatly enhanced the protective properties of the epoxy coating, retarding electrolytes absorption and reducing the total amount of adsorbed water. The latter occurrence suggests that the graphene effect on coating performances is related to both extended diffusion pathway length and graphene/matrix interaction due to the unique properties of graphene.

Selected Cr(VI) replacement options for aluminum alloys: a literature survey

Abstract There is a significant move away from the use of hexavalent chromium, Cr(VI), which is a mature, trusted, and relatively inexpensive treatment that has been used for many years by industry to reduce corrosion. Although Cr(VI) is effective at reducing corrosion, it poses a substantial health hazard. While there is a need to define a process that will be able to replace Cr(VI), the process must be able to provide the same level of corrosion protection currently provided by hexavalent treatments. In addition, it needs to do this without the associated environmental problems. This paper focuses mainly, but not exclusively, on the trivalent chromium pretreatment (TCP) and its commercially available variants. The TCP was developed by the Naval Air Systems Command (NAVAIR) and is used by the US military. The rationale for the focus of this paper is that in the near term, the aeronautics industry needs to move away from Cr(VI) towards a more benign commercially available chemical treatment that can help protect the aluminum alloys used by that industry. TCPs are currently available commercially and have undergone numerous tests by multiple organizations to establish their effectiveness in reducing corrosion of both bare and painted aluminum alloys.

Loss of Adhesion at Al 8006/LDPE Interface in Containers for Food Packaging: A Case Study

A company recently reported, the unexpected and sudden failure of several containers, fabricated from aluminium 8006 and sealed using a polymeric film. The failure resulted when there was a loss of adhesion at the metal/polymeric lid interface, making the containers unusable. Some preliminary adhesion tests have highlighted that, containers, coming from various production batches and sealed using the same kind of lid, exhibited different adhesion strengths. To investigate the cause of the detachment of the lid from the edge of the container, the following parameters has been considered: (i) the iron content of the Al alloy, (ii) the effect of lubricant oil at the polymeric film/substrate interface, (iii) the topography of the contact surface between the lid and the container. The electrochemical behaviour of Al8006 was investigated by means of potentiodynamic polarization tests, both in an aerated aqueous solution of Na2SO4 (0.5 M) and in an aerated aqueous solution of NaCl (0.6 M). The results revealed a significant increase in corrosion rate for the samples with higher iron content, as well as the negative influence of oil on the surface. Roughness measurements have confirmed the importance of the surface profile: a surface showing Sku>3, provides better adhesion. Metallographic measurements demonstrated that high iron content in the alloy results in the development of numerous corrosion spots and prevents good adhesion between the sealant polymeric film and the aluminium foil.