In situ microscopic investigation of ion migration on the surface of chromium coated steels

Cathodic spreading of electrolyte on two-layers chromium coatings electrodeposited from trivalent chromium electrolyte on steel was studied on the micro- and the macroscale. The behavior is discussed in view of results obtained on electrical conductivity as measured by current-sensing atomic force microscopy. The coatings were found to hinder electron transport. Heterogeneities observed in the electrical conductivity are correlated to heterogeneities of the electrolyte spreading behavior, studied using in situ scanning Kelvin probe force microscopy. In average, the kinetics of spreading observed at microscopic scales are similar to that observed using a scanning Kelvin probe at larger scales. The scanning Kelvin probe force microscopy is demonstrated as a robust in situ technique to follow electrolyte spreading and study microscopic defects/heterogeneities on the surface

Importance Sampling for Credit Risk Monte Carlo Simulations using the Cross Entropy method

For this thesis, we applied the Cross Entropy method on a credit risk model for the ING wholesale lending portfolio and some synthetically created realistic portfolios. The Cross Entropy method is found to be able to find appropriate Importance Sampling parameters within a relative modest resource budget. With the new parameters, the standard deviation of the estimate that the losses will exceed the available buffer can be decreased with more than 95%. A similar reduction with regular Monte Carlo would require the number of scenarios to increase four hundred times. Alternative methods provide similar reductions, but these use numerical methods that are more complex to implement and require more resources to calculate. Further tests show that the method is robust to the parameters used in the Cross Entropy method (within reasonable limits), it is not influenced significantly by the constitution of the portfolio and that none of the problems occur that the scientific literature warns about (in particular the “degeneracy of the likelihood ratio”)

The Kinetics and Mechanism of Atmospheric Corrosion Occurring on Tin and Iron-Tin Intermetallic Coated Steels: II. Filiform Corrosion

This paper describes a systematic study into the initiation and propagation of filiform corrosion (FFC) on pure iron, pure tin and industrially important tin and iron-tin intermetallic (FeSn and FeSn2) coatings for packaging steels, as a function of coating weight. The time-dependent extent of FFC was determined optically. FFC was not observed on pure tin or tin coatings but was found to propagate at significantly reduced rates on the FeSn and FeSn2 intermetallic coatings, when compared to pure iron. An explanation of the findings is given, firstly, in terms of the open circuit potential (OCP) and the extent to which polarity of the galvanic corrosion cell formed between relevant phases permits FFC propagation, and secondly in terms of the relative susceptibility of the various phases to anodic dissolution. It is concluded that even when FFC is feasible thermodynamically, propagation rates may be negligible due to the low activity for anodic dissolution of tin and iron-tin intermetallics

Covalent polymer functionalization of graphene/graphene oxide and its application as anticorrosion materials

Research on grapheme-polymer composites as the promising ion barrier materials to tackle the corrosion issue is rapidly developing and attracts interests from both academia and industry. In this minireview, we highlight the covalent functionalization of graphene and its derivatives such as graphene oxide (GO) with polymer brushes, and their application in anticorrosion within the last 3 years. There are some recent excellent reviews published on single layer graphene and graphene-based polymer composites for anticorrosion. However, the covalent functionalization of graphene and GO with polymer brushes for application in anticorrosion has not been addressed in those reviews. In this review, we describe first the current state of the art of covalent functionalization of graphene/GO with polymer brushes. We then discuss the application of pristine graphene as anticorrosion material and its drawbacks which can be overcome by graphene-based polymer composites. Afterwards, we discuss in detail the recent progress and development of covalent polymer functionalized graphene/GO as anticorrosion coatings, reported within the last 3 years. Finally, as perspective, we will briefly summarize the work on composites of polymers with other two-dimensional (2D) materials as anticorrosion coatings. Herein, hexagonal boron nitride, the most studied 2D materials after graphene, and Ti3C2Tx MXene which is the rising star of 2D transition metal carbide/nitride will be discussed

Ti₃C₂T_<i>x</i>MXene Polymer Composites for Anticorrosion:An Overview and Perspective

[Image: see text] As the most studied two-dimensional (2D) material from the MXene family, Ti(3)C(2)T(x) has constantly gained interest from academia and industry. Ti(3)C(2)T(x) MXene has the highest electrical conductivity (up to 24,000 S cm(–1)) and one of the highest stiffness values with a Young’s modulus of ∼ 334 GPa among water-dispersible conductive 2D materials. The negative surface charge of MXene helps to disperse it well in aqueous and other polar solvents. This solubility across a wide range of solvents, excellent interface interaction, tunable surface functionality, and stability with other organic/polymeric materials combined with the layered structure of Ti(3)C(2)T(x) MXene make it a promising material for anticorrosion coatings. While there are many reviews on Ti(3)C(2)T(x) MXene polymer composites for catalysis, flexible electronics, and energy storage, to our knowledge, no review has been published yet on MXenes’ anticorrosion applications. In this brief report, we summarize the current progress and the development of Ti(3)C(2)T(x) polymer composites for anticorrosion. We also provide an outlook and discussion on possible ways to improve the exploitation of Ti(3)C(2)T(x) polymer composites as anticorrosive materials. Finally, we provide a perspective beyond Ti(3)C(2)T(x) MXene composition for the development of future anticorrosion coatings

The corrosion of chromium based coatings for packaging steel

Chromium/chromium oxide based coatings, cathodically electrodeposited from either Cr (VI) or Cr (III) containing electrolytes are compared with respect to their ability to resist the corrosion driven delamination of an adherent polymer overcoat. Cathodic disbondment rates are determined using an in-situ scanning Kelvin probe technique. Anodic disbondment (filiform corrosion, FFC) rates are determined optically. The Cr (VI) derived coatings were fully resistant to corrosion driven disbondment. The Cr (III) derived coatings exhibited measurable rates of both FFC and cathodic disbondment. Disbondment kinetics are explained in relation to coating morphology, porosity and chemical composition determined using a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and xray photoelectron spectroscopy (XPS)

Inter-layer Adhesion Performance of Steel Packaging Materials for Food Cans Under Retort Conditions

The steel packaging industry faces the dual challenge imposed by legislation to eradicate the use of Chrome(VI) from sub- strate manufacture and the removal of Bisphenol-A (BPA) from the organic lacquer at the point of food contact. The paper reports on an experimental investigation into the quality of adhesion between the coatings and substrates as a result of the retort process, typically the harshest conditions to which the materials will be exposed. In terms of adhesion, the novel Chrome(III) substrates show promise when compared with current Chrome(VI) substrate. There is a significant reduction in the adhesion of the polyester-based Bisphenol-A non-intent lacquers compared to the incumbent epoxy-phenolic lacquers. Adhesion performance is lower with an increase in retort temperature and time of exposure. The adhesion further reduces in mild acidic and saline conditions. The reduction in adhesion post-retort is attributed to the sensitivity of the polyester-based BPANI lacquers to water vapour absorption. The process reversible nature of the adhesion loss indicates that, at short time- scales, the adhesion loss is a result of polyester hydrolysis. Acidic and saline solutions also lead to a reduction in adhesion as a result of metal surface corrosion. The paper has impact on producers, fillers and consumers of steel packaging foodstuff