Understanding the role of snout contamination in the formation of an oxide based defect in hot dip galvanised coating

Due to increased demand for defect free, quality critical outer panel material for the automotive sector, continued focus on zinc coating quality is required. The snout area of a continuous galvanizing line is often a major source of coating issues with various surface defects arising from poorly understood and uncontrolled snout practices. This paper investigates the formation of a snout defect termed ‘the arrowhead defect’, named after its characteristic arrowhead shape. Defective samples have been characterised with the use of SEM/EDX and XRD and compared with contaminated sources collected from within the continuous galvanizing line snout. It is common practice to inject wet HNx into the snout in order to inhibit the production of zinc vapour. The wet HNx promotes the for- mation of a ZnO layer on the surface of the liquid zinc bath, preventing vaporisation and thereby reduces zinc dust contamination. The presence of ZnO, deliberately formed through the injection of wet HNx into the snout was observed within the arrowhead defect and can be identified as the root cause of this defect. Discrete contam- ination particles were entrained within the tail of the defect. XRD patterns of both the defect & snout contamina- tion have been presented to discern the nature of the contamination entrained within the zinc coating. Characteristic ZnO peaks were observed at θ = 32° for both surface contamination and at increasing penetration depths within the coating in the region of the arrowhead defect. The inclusion of the arrowhead defect in Full Finish material led to an increase in the rate of corrosion 2.5× that of the corrosion rate on non-defective mate- rial, highlighting the need to produce defect free galvanized steel for both aesthetic and corrosion purposes. Whilst the injection of wet HNx as a method of suppressing the formation of zinc vapour is a long standing pro- cess for automotive Full Finish production, due to the nature of these oxide-based defects, this process is in fact a “double edged sword” in that it solves one problem but can create another. Alternative techniques to suppress zinc vapour formation should be investigated to further drive up the quality of zinc coatings for automotive applications

A fossil ray spider (Araneae: Theridiosomatidae) in Cretaceous amber from Vendée, France

A new species of fossil ray spider, Baalzebub? mesozoicum n. sp. (Araneae: Theridiosomatidae), is described from Mesozoic amber from the Cretaceous (Middle Cenomanian to Early Santonian) deposits of La Garnache, Vendée, NW France. The palpal structures, especially the highly sclerotized claw-shaped retrolateral ‘paracymbium’ originating as an outgrowth of the cymbium basally and the basal cymbial lamella, are considered sufficient to make a tentative placement of the new fossil species in the extant genus Baalzebub Coddington, 1986

Effect of intercritical annealing on the mechanical properties of dual-phase steel

A dual-phase steel chemistry has been processed with varying intercritical annealing temperatures and the properties investigated. It was found that increasing the temperature in the intercritical region led to an increase in the volume fraction (52%–65%) and grain size (1.8–3.3 µm) of martensite whilst the volume fraction and grain size of ferrite decreased. The highest tensile strengths were found at low intercritical temperatures, achieving 935 MPa whilst the highest elongation values of 21% were achieved at the highest intercritical temperatures

The Holocene Marine Sequence in the Løkken Area of Vendsyssel, Denmark

Jessen (1918, 1920, 1936) postulierte die Existenz einer Landbrücke, die das Løkken-Gebiet während des Holozän vom Skagerrak trennte, und Mörner (1969) deutete an, daß drei aufeinanderfolgende positive Seespiegel-Verschiebungen, die seinen PTM-2, PTM-3 und PTM-4 Strandlinien entsprechen, das Gebiet überflutet haben. Neue Befunde, die sich weitgehend auf einen Vergleich von Mikrofossil-Daten (Diatomaceae, Foraminifera und Ostracoda) stützen, bestätigen Jessens Ansicht. Marine Verhältnisse breiteten sich zwischen 8000 v. h. und 5300 v. h. von Süden her vordringend im Løkken-Gebiet aus, und es erfolgte kein Zustrom von stärker salzhaltigen Wässern aus dem Westen. Widerspruchsfreie Beweise für Seespiegelschwankungen wurden jedoch nicht gefunden.researc

Fine structural analysis of the intact adrenal cortex and of regenerating intramuscular adrenocortical transplants in the rat

Thesis (Ph.D.)--Boston UniversitySeveral investigators have reported on the fine structure of the normal adrenal gland of the rat using electron microscopy, and many have described the changes which occur during the processes of regeneration of both enucleated and transplanted adrenal glands, using a variety of histochemical techniques for subsequent analysis by optical microscopy. Since the larger inclusions, such as intracellular lipid droplets, have been followed through the stages of regeneration (Brenner, et al, 1953), an attempt was made in this investigation to analyze the changes in cytoplasmic organelles during the process of regeneration, utilizing the electron microscope, and to correlate the observations with those of the regenerating adrenal gland that have been reported using optical microscopy. Experimental Procedure Male albino rats of the Wistar strain, weighing between ninety-five and one hundred fifty grams were bilaterally adrenalectomized by the dorsal approach under ether anesthesia. The right adrenal glands were either used for control purposes or discarded. The left adrenal gland was bisected and autotransplanted into pockets made in the dorsal musculature. All animals were given Purina Laboratory Chow ad libitum and a one percent saline drinking water for a period of seven days post-operatively, after which tap water was given. These animals were sacrificed and their transplants removed after two, four, seven, fourteen, twenty-one, and sixty days of regeneration. Tissue specimens of one cubic millimeter size were fixed for two hours in cold one percent osmium tetroxide buffered to pH 7.2 with veronal-acetate buffer, after which they were dehydrated and embedded in either methacrylate monomers or epoxy resin. After curing the plastic in an oven, sections of three hundred to eight hundred Angstrom units thickness were cut on a Porter-Blum microtome, placed on carbon coated copper grids, which has previously been covered with a thin layer of Formvar, and observed in an RCA EMU Microscope, Model 3B, at fifty kilovolts. Normal control animals were sacrificed and their left adrenals processed in the same manner as above [TRUNCATED

The effect of ultrasonic irradiation on the microstructure and corrosion rate of a Zn–4.8wt.% Al galvanising alloy used in high performance construction coatings

The microstructure and corrosion resistance of a Zn–4.8 wt.% Al alloy, typically used for high performance galvanised coatings for construction, was modified by the application of ultrasound during solidification. The alloy exposed to ultrasound had an increased volume fraction of smaller, discrete primary η Zn phase regions that were more uniformly distributed throughout the casting. The morphology of η Zn was altered from dendritic to globular and the Zn/Al eutectic growth was disrupted in localised areas from lamellar to anomalous. These changes were likely due to the physical action of the ultrasound disrupting compositional effects, fragmenting dendrites and through the development of cavitation events causing disruptive mixing. These microstructural changes produced an enhanced cut-edge corrosion resistance of the alloy in 0.1% NaCl when coupled with steel mimicking in service coating conditions that was investigated using the SVET. The primary η Zn crystal regions were focussed sites for anodic Zn dissolution and the smaller η regions produced by ultrasound reduced the corrosion rate by preventing the development of crevice like phenomena that may be associated with larger dendrites. The number and size of primary η Zn regions affected the corrosion rate with reductions in these factors reducing the corrosion rate of the alloy

The Role of pH on the Inhibition of Aqueous Zinc Corrosion by L-tryptophan

A combination of in situ Scanning Vibrating Electrode Technique (SVET), and time lapse photography were used to investigate the influence of the amino acid, L-tryptophan, on the localized corrosion occurring on unpolarized zinc (Zn) samples immersed in a 0.17 mol.L−1 aqueous sodium chloride electrolyte. The addition of 1 × 10−2 mol.L−1 of L-tryptophan was found to have a significant effect on the corrosion rate for all pH values tested. At both pH 2 and pH 7, primary protection was suggested to occur as a result of adsorption due to electrostatic interactions. A secondary mechanism, whereby an insoluble complex is formed between Zn (II) ions and anionic L-tryptophan, was also proposed to occur at areas of localized high pH. At pH 2 the additions resulted in an 88% decrease in mass loss, as measured by gravimetric mass loss results and SVET, demonstrating the effectiveness of L-tryptophan inhibitors for this material

Curriculum reform in Wales: Physical education teacher educators\u27 negotiation of policy positions

This paper reports on research that explored the experiences of secondary Physical Education Teacher Education (PETE) professionals\u27 simultaneous negotiation and implementation of the new Curriculum for Wales (CfW) Health and Well-Being (HWB) Area of Learning and Experience (AoLE) and policies focused on the transformation of Initial Teacher Education (ITE) in Wales. The study was an exploratory case study of PETE professionals working within one university\u27s ITE programme. Data were generated through documentary analysis of PETE and ITE programme materials and semi-structured interviews with staff involved in programme management and delivery. Data analysis employed Ball and colleagues\u27 conceptualisation of policy actors and contexts to critically examine the varied policy positions that PETE professionals adopt in navigating and negotiating enactment of the HWB AoLE within their ITE provision. Attention is drawn to the significance of historical and culturally situated dimensions of secondary physical education and PETE in Wales, and significant changes to the professional culture of ITE, in shaping PETE educators\u27 engagement with the HWB AoLE. The paper concludes by contending that ITE institutions in Wales need to further consider how PETE (and other) educators can be actively supported to engage in sophisticated policy work within their institutions and across policy and professional networks

Al2O3 Coatings for Protection of Stainless Steel 316L against Corrosion in Zn-Al and Zn-Al-Mg

The production and quality of automotive-grade galvanised steel are affected by the limited service life of the pot roll bearings used in continuous galvanising lines. The journal bearings are subjected to severe degradation as they react with the molten Zn bath, and coatings can provide corrosion protection to the bearing materials. This research investigates the performance of Al2O3 coatings applied via the HVOF thermal spray process to stainless steel 316L substrates. Immersion tests were conducted in baths of different compositions, namely GI (Zn-0.3 wt.% Al) and ZMA (Zn-1.5 wt.% Al-1.5 wt.% Mg). Material characterisation after testing showed evidence of coating degradation after 1 week, as the coating tended to crack and detach from the substrate, allowing the molten Zn to attack the underlying steel. The coefficient of thermal expansion of Al2O3 and steel was measured, and a difference of 13 × 10−6 K−1 was found, leading to the development of cracks in the coatings. Zn penetration through cracks was determined to be the main failure mechanism of the Al2O3 coatings, which otherwise remained inert to Zn-Al. Conversely, the coatings immersed in Zn-Al-Mg reacted with the Mg in the molten metal bath, showing that changing bath composition affected the performance of the coatings in molten Zn alloy