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

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

Chromium coatings from trivalent chromium plating baths: Characterization and cathodic delamination behaviour

Novel two-layer chromium-based coatings comprised of a first layer containing chromium, oxygen and carbon (Cr-O-C) and an oxygen rich (Cr-O) topcoat were electrodeposited from trivalent chromium electrolyte. The complex structure and composition of the coatings were studied using complementary characterization techniques. The electrodeposited oxide was found to be amorphous and oxygen-deficient. In operando ambient pressure X-ray photoelectron spectroscopy when heating the sample from room temperature to 450 °C and Raman spectroscopy after the heating ascertained the metastable nature of the oxide. The cathodic delamination of a weak model polymer on these samples was studied using in situ scanning Kelvin probe. © 2021 The Author(s

A rapid method for immunotitration of influenza viruses using flow cytometry

Reliable assays for accurate titration of influenza virus in infectious samples are pivotal to both influenza research and vaccine development. A titration assay adopted commonly for this purpose is the plaque assay on Madin-Darby canine kidney (MDCK) cells, despite it being time and labour consuming. A novel assay is described for titration of influenza viruses based on the detection of intracellular viral nucleoprotein (NP) by fluorescence-activated cell sorting (FACS). By using a panel of viruses of different type, subtype and origin, it is demonstrated that there is a mathematical correlation between titres measured by immunotitration and by classical plaque assay on MDCK cells. Moreover, the availability of NP antibodies specific for type A or type B influenza virus ensures the specificity of the assay. Based on speed, accuracy and specificity, it is concluded that the FACS-based immunotitration of influenza virus represents a valid and efficient alternative to the classical plaque assa