Publications

We present fiber Bragg grating based transversal load sensing with a highly birefringent microstructured optical fiber. For the bare fiber, the change of the Bragg peak separation under a transverse line load was simulated with a finite-element model and experimentally verified. We also show that microstructured optical fibers with fiber Bragg gratings can be successfully embedded in a carbon fiber reinforced composite material. The linear dependence of the Bragg peak separation to a transversal stress in the composite sample was measured to be 15.3 pm/MPa.

Atmospheric corrosion of metals is the most common type of corrosion which has a significant impact on the environment and operational safety in various situations of everyday life. Some of the common examples can be observed in land, water and air transportation systems, electronic circuit boards, urban and offshore infrastructures. The dew drops formed on metal surface due to condensation of atmospheric moisture facilitates corrosion as an electrolyte. The corrosion mechanisms under these droplets are different from classically known bulk electrolyte corrosion. Due to thin and non-uniform geometric thickness of the droplet electrolyte, the atmospheric oxygen requires a shorter diffusion path to reach the metal surface. The corrosion under a droplet is driven by the depletion of oxygen in the center of the droplet compared to the edge, known as differential aeration. In case of a larger droplet, differential aeration leads to preferential cathodic activity at the edge and is controlled by the droplet geometry. Whereas, for a smaller droplet, the oxygen concentration remains uniform and hence cathodic activity is not controlled by droplet geometry. The geometry of condensed droplets varies dynamically with changing environmental parameters, influencing corrosion mechanisms as the droplets evolve in size. In this review, various modelling approaches used to simulate the corrosion under droplet electrolytes are presented. In the efforts of developing a comprehensive model to estimate corrosion rates, it has been noted from this review that the influence of geometric evolution of the droplet due to condensation/evaporation processes on corrosion mechanisms are yet to be modelled. Dynamically varying external factors like environmental temperature, relative humidity, presence of hygroscopic salts and pollutants influence the evolution of droplet electrolyte, making it a complex phenomenon to investigate. Therefore, an overview of available dropwise condensation and evaporation models which describes the formation and the evolution of droplet geometry are also presented from an atmospheric corrosion viewpoint.

This work presents the synthesis of nanostructured hollow polyaniline (PANI) capsules and their application for encapsulation of corrosion inhibitor 2-Mercaptobenzothiazole (MBT). The pH-triggered release of MBT from the capsules was evidenced using UV–vis and Surface Enhanced Raman Spectroscopy (SERS). Incorporation of MBT loaded PANI capsules into epoxy ester coating on AA2024-T3 resulted in a protective system with self-healing ability confirmed by Electrochemical Impedance Spectroscopy (EIS) and Scanning Vibrating Electrode Technique (SVET). The results showed that the incorporation of MBT-loaded PANI capsules into the coating has significantly improved its corrosion protection performance due to the interesting smart characteristics of PANI capsules.

A 2D finite element model is developed to simulate the protection of active protective coatings in a defect. The leaching kinetics, inhibitor-electrolyte reactions and electrochemical surface reactions on homogenized AA2024-T3, are considered. Changes in local oxygen distribution, pH, and current density over time are validated using surface scanning micro-probe techniques. The limitations posed by the prediction of surface current density at the metal interface using a FEM model with a homogenized microstructure are identified and addressed. The validated FEM is then used to predict inhibitor concentration and pH dependent on the initial inhibitor pigment concentration in an organic coating.

Many efforts have been made to describe and control the formation of polypyrrole layers on iron. The corrosion protection performance of these layers has been greatly improved through the variation of their bulk properties such as the size of the counter-ions or the inclusion of metallic oxide nanoparticles. In this work, the properties of the iron/polypyrrole interface have been varied through a set of iron surface pre-treatments. Surface analysis techniques allowed to monitor this variation, which proves to have a strong influence on the corrosion protection performance of polypyrrole-coated iron. A clear correlation could then be established with the electrochemical impedance spectroscopy (EIS) data by modelling the system with an equivalent circuit. The properties of the iron/polypyrrole interface were quantified and this quantification was confirmed experimentally by the use of a mercury cell.

This work deals with the plasma‐deposition of allyl methacrylate (AMA) and acrylic acid (AA) on metallic substrates. The plasma setup used is an atmospheric pressure radio frequency (RF) torch. Infrared reflection absorption spectroscopy (IRRAS) and X‐ray photoelectron spectroscopy (XPS) are used as characterization tools. In addition, spectroscopic ellipsometry (SE) has been used to control the thickness and calculate the corresponding deposition rates. Whereas the surface chemistry of plasma deposited AMA does not seem to be influenced by the plasma power, acrylic acid based coatings are strongly degraded with the increasing power. AMA seems to allow an efficient polymerization, while at the same time is particularly resistant to plasma induced fragmentation in the range of power used. magnified image

No abstract is provided for this article.

Allyl methacrylate (AMA), methyl methacrylate (MMA), and propyl isobutyrate (PiB) are plasma deposited at ambient temperature in an atmospheric DBD reactor to assess the effect of precursor carbon double bond unsaturations. The specific plasma deposition rate (k0) as a function of the Yasuda factor (Yf) is quantified empirically by: k0 = b (1 − exp(–a Yf/b)). Fourier transform infrared analysis indicates a loss of carbonyl functionalities with increasing plasma power, and Raman microscopy shows CC double bonds in all plasma films. The methacrylate-like plasma films are found to be heterogeneous with a volatile and a cross-linked fraction observed by thermogravimetric analysis. Differential scanning calorimetry reveals a low glass transition temperature and a characteristic residual reactivity of the coatings.

Cr-C coatings were obtained from two different Cr(III)-baths based on sulphate and chloride salts, respectively. A tailored characterization was carried out by scanning electron microscopy, several spectroscopies and Mott-Schottky approaches (including Point Defect Model) to find out the impact in the corrosion performance of the morphology, composition, and semiconducting properties of the native oxide layers. The polarisation curves using 0.01 M NaCl have shown better corrosion resistance capabilities for the chloride-based Cr(III) coatings which is in agreement with the lower crystal size and the less defective native oxide layer (using a borate buffer electrolyte).

We have successfully obtained surfactant-free latexes from anhydride-containing polymers, including poly(styrene-alt-maleic anhydride) (PSMA), maleinized polybutadiene (PBDMA), and poly(octadecene-alt-maleic anhydride) (POMA). Here we report barrier and adhesion properties of the coatings made from these surfactant-free latexes, which were crosslinked with adipic acid dihydrazide (ADH). The barrier property of these coatings was studied with electrochemical impedance spectroscopy in NaCl solutions on pretreated aluminum substrates. PSMA and PBDMA-based coatings demonstrated good barrier property, indicated by the absence of corrosion after 1-month immersion in NaCl solutions, which was comparable to that of a commercially available polyester coating. The polyester coating, however, was found to hydrolytically degrade when immersed in a NaCl solution, which was not observed for our latex-based coatings. The POMA-based coating showed inferior barrier property on un-pretreated aluminum, likely due to inhomogeneous film formation and poor adhesion to the substrate, but the adhesion could be improved by an alkali pretreatment of the substrate. In comparison, PBDMA and PSMA-based coatings showed much better adhesion toward the aluminum substrates. The anti-corrosion behavior appeared to be closely related to both the barrier and adhesion properties of the coatings on the metal substrate.

The stability of polyurethane/iron oxide/steel interfaces was evaluated for different chemically modified passive films in humid and corrosive atmosphere. Iron oxide layers were formed on polished steel by thermal annealing in oxygen rich atmosphere, water plasma modification, immersion in alkaline solution and by anodic polarisation in borate buffer solution. Scanning Kelvin Probe studies of the interface stability were performed under the conditions of cathodic delamination. The corresponding progress rates specifically depended on the iron oxide. Complementary measured peel-off forces of the respective coating/substrate systems showed the same trend as detected for the corrosive delamination process. Additional contact angle measurements and investigation of the interfacial ion mobility on the uncoated oxide surfaces confirmed a correlation between high peel forces, increasing oxide surface energy and decelerated cathodic delamination kinetics.