Instantly Investigating the Adsorption of Polymeric Corrosion Inhibitors on Magnesium Alloys by Surface Analysis under Ambient Conditions

Abstract

Surface engineering of magnesium alloys requires adequate strategies, processes and materials permitting corrosion protection. Liquid formulations containing corrosion inhibitors often are to be optimized according to the demands of the respective substrate and following the service conditions during its application. As an interdisciplinary approach, a combination of several techniques for instantly monitoring or elaborately analyzing the surface state of magnesium was accomplished in order to characterize the performance of new adsorbing sustainable amphiphilic polymers which recently were developed to facilitate a multi-metal corrosion protection approach. The application of established techniques like Contact Angle measurements and X-ray Photoelectron Spectroscopy investigations was supplemented by introducing related and yet faster online-capable and larger-scale techniques like Aerosol Wetting Test and Optically Stimulated Electron Emission. Moreover, an inexpensive setup was configured for scaling the inset and the extent of degradation processes which occur at local electrochemical circuits and lead to hydrogen bubble formation. Using these analytical tools, changes of the surface state of emeried AM50 samples were investigated. Even in contact with water, being a moderate corrosive medium, the online techniques facilitated detecting surface degradation of the unprotected magnesium alloy within * Corresponding author. L. M. G. Gonçalves et al. 283 some seconds. In contrast, following contact with a 1 weight% formulation of a polymeric corrosion inhibitor, surface monitoring indicated a delay of the onset of degradation processes by approximately two orders of magnitude in time. Mainly based on the spectroscopic investigations, the corrosion inhibiting effects of the investigated polymer are attributed to the adsorption of a primary polymer layer with a thickness of a few nanometers which occurs within some seconds. Immersion of magnesium for several hours brings up a protective film with around ten nanometers thickness.

Interfactant action of an amphiphilic polymer upon directing graphene oxide layer formation on sapphire substrates

“…carbonaceous moieties with a concentration around 20 at % as indicated by the XPS measurements. The contact angle found for the G50-17 h sample results similar to the one reported by Gonçalves et al [5] for a G50 film formed on a magnesium alloy surface. The microscopic findings for the surface structure of pristine sapphire surfaces and the G50-17h sample as obtained by SFM investigations are presented in Fig.…”

“…Two dominant C1s peaks centered around 285 and 287 eV are attributed to hydrocarbonaceous species with C*-H or C*-C bonds and, respectively, to species with C*-O single bonds. On a molecular level, these ones are assigned to polyoxyalkylene moieties in G50-based polymers and to functional groups in graphene oxide, like carbon-bonded hydroxyls, phenols, ethers, or epoxy moieties [5,28]. As a consequence, the adsorption of moieties from the GO dispersion will be inferred from evaluating the attenuation of the sapphire-related Al2p XPS signal intensity, from contact angle measurements, and from SFM investigations.…”

“…The effective polymer will be denoted as "G50" throughout this contribution. Properties of the polymer formulation were described elsewhere [5,6]. Based on a parent formulation containing 4 wt% of organic constituents comprising polymer and triethanolamine (TEA) for adjusting the pH value, diluted formulations with a concentration of 2 wt% were prepared by adding demineralized water to the parent formulation.…”

“…As it was shown for amphiphilic polymers, such non-linear shape may result from intramolecular interactions, a phenomenon which is quite common also for polypeptides, e.g. globular proteins [4][5][6]. Especially for such polymeric monolayers the term polymeric interfactant layer was suggested recently [6].…”

Implementation of diverse non-centrosymmetric layer concepts for tuning the interface activity of a magnesium alloy

“…We will investigate the concentration-dependent Fig. 1 Sketches of multilayer systems forming an adhesive joint of identical adherents in the geometry of a lap-shear test specimen (a), and a non-centrosymmetric coating system (b) on a substrate adsorption behavior of a synthetic amphiphilic polymer [12] and the interaction between a magnesium alloy substrate and an aqueous biopolymer mixture containing the nanoparticulate enzyme laccase, similar to the formulation recently described in an interaction with acidic silicon oxide surfaces [13]. Thin films containing biopolymers recently were tested with respect to improving the corrosion resistance of magnesium alloys [14,15].…”