Thesis (Ph. D.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains xi, 106 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 101-106).

Thesis (Ph. D.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains xx, 272 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 207-208).

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains vii, 83 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 80-82).

<p> The selective surface oxidation of alloying elements such as Mn can cause dual phase (DP) steel wettability problems by liquid Zn during continuous galvanizing. It is well known that process parameters, such as the annealing atmosphere %H2 and dew point, can affect surface and subsurface oxidation. The purpose of this research was to study the effect of the annealing atmosphere to determine the optimum DP steel surface that would result in better reactive wetting by zinc. In particular, the evolution of the surface phases and structures during the continuous galvanizing annealing cycle were studied. It was shown that the internal I external oxidation behavior of the alloying elements of DP steel (e.g. Mn and Mo) at the surface and subsurface can be controlled by changing process parameters (dew point and H2/N2 ratio) and that some segregation of elements is unavoidable but can result in good reactive wetting by liquid galvanizing alloys. A transition from external to internal oxidation was observed when the oxidation potential (pH20ipH2) of the annealing atmosphere was increased from 0.00844 to 0.03451. Despite the presence of 9-19 wt% Mn as MnO in the pre-dipped steel surface, the coatings exhibited good adhesion and a well developed Fe2Als inhibition layer at the coating I substrate interface for all experimental annealing atmospheres as a result of reactive wetting. This is attributed to aluminothermic reduction of manganese oxide by aluminum present in the liquid galvanizing alloy. </p> / Thesis / Master of Applied Science (MASc)

Narrow gaps in overlapping structural steel surfaces are problematic when being hot-dip galvanized due to the potential for trapped cleaning solutions between the surfaces. A seal-weld is often used to prevent the cleaning solutions from penetrating this gap. However, these welds are not necessary used for strength, and add fabrication costs because of the additional weld. The purpose of this research is to provide alternatives, which fall under two major categories, to the seal-weld fabrication process. The first one was motivated by the steel fabrication industry and uses a commercial silicone caulk to seal the narrow gap instead of a seal-weld. The second was motivated by the galvanizing industry and increases the narrow gap to a minimum of 3/32 in. to allow free flowing of the liquids including viscous molten zinc. 45 specimens in six different overlapping configurations were tested. Three experimental tasks were performed as part of this research: two different types of silicone caulks were used to partially substitute the seal-weld to prevent fluid penetration; an accelerated corrosion test was performed to determine the long-term corrosion resistance of each configuration; and a coating layer evaluation was performed to investigate the bond of the metallurgical layer between the steel and the coating. Results indicate that silicone only partially prevented the penetration of the cleaning solutions into the gap but performed poorly when fully galvanized. Also, the accelerated corrosion and coating investigations indicated that the suggested caulks and the 3/32 in. gap were not as efficient as the seal-weld solution. / Master of Science

O objetivo deste trabalho visa analisar criticamente o processo de fabricação do arame galvanizado, discutindo a influência de variáveis, tais como: composição química do aço, velocidade dos fios na linha de galvanização e temperaturas associadas ao tratamento térmico, garantindo com isto um produto aderente as novas necessidades apresentadas pelo setor da avicultura que emprega o arame galvanizado BWG 18 na confecção de telas. A metodologia adotada envolveu as etapas de revisão da literatura e procedimento experimental D.O.E. (Design of Experiments), com coleta de amostras sob diferentes empregos (matéria prima) e condições operacionais (alteração de velocidades na linha de galvanização) e posterior realização de ensaios e análises de laboratório nas amostras coletas. Na etapa final foi realizado a avaliação e discussão dos resultados obtidos, identificando o produto galvanizado que melhor atende as propriedades mecânicas exigidas na fabricação de telas para o setor de avicultura. / The objective of this work aims at critically analyze the process of manufacture of the galvanized wire, arguing the influence of variables, such as: chemical composition of the steel, wire speed in the galvanizing line and temperatures associates to the heat treatment, ensuring with this an adherent product the new necessities presented for the poultry keeping that uses galvanized wire BWG 18 in the manufacturing of wire mesh. The adopted methodology involved the stages of revision of literature and experimental procedure D.O.E. (Design of Experiments), with acquisition of samples under different jobs (raw material) and operational conditions (alteration of speeds in the galvanizing line) and later accomplishment of assays and analyses of laboratory in the samples collections. In the final stage it was carried through the evaluation and quarrel of the acquired results, identifying the galvanized product that better takes care of the demanded mechanical properties in the manufacture of wire mesh for the poultry keeping sector.

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Materials Science, 2006. / Includes bibliographical references.

The major concern regarding the use of hot-dip galvanized (HDG) steel as reinforcement in concrete has been the high rate of corrosion experienced by the zinc during the first hours in the fresh, wet, and highly alkaline concrete. The present work was aimed at clarifying three issues associated with these concerns. The first involves the metallurgical phases at the surface of the zinc coating. The concentration of zinc at the surface is a function of processing procedures, surface treatment, and exposure to weathering. Differences in the coating surface composition influence the corrosion behaviour of HDG steel reinforcing bars when they are embedded in concrete. The second issue involves the increasing use of supplementary cementing materials in concrete, which change the chemistry of the concrete pore fluid, and also influence the corrosion. The third issue is that the initial corrosion is accompanied by hydrogen evolution, which could increase the pore volume of adjacent cement and thereby, decrease the bond stress between the concrete and the steel. In order to limit the hydrogen evolution, a chromate layer is applied after galvanizing. The results of the project have demonstrated that, during zinc corrosion in ordinary Portland cement (OPC) concrete, calcium hydroxyzincate formed on untreated HDG steel provided sufficient protection against corrosion. Therefore, it is concluded that treating HDG rebar with dilute chromic acid is unnecessary as a method of passivating zinc. A layer of zinc oxide and zinc carbonate formed through weathering on HDG bars slightly increased the initial corrosion rate and passivation time compared with the non-weathered rebars. HDG steel with an alloyed coating, i.e. consisting of Fe-Zn intermetallic phases, required a longer time to passivate than those with a pure zinc surface layer. The lower zinc content of the surface limited the rate of CHZ formation and, hence, delayed passivation. However, regardless of the surface condition, the coating depth loss after two days of embedment in OPC concrete was insignificant. In concretes containing 8% cement replacement with silica fume, or 25% cement replacement with slag, the initial corrosion rates were higher than those in OPC due to higher pH and lower calcium contents of the concrete pore solution. The higher corrosion rates lead to initial depth losses which are considered significant. However, in these concretes, chromate treatment was also shown to be unnecessary. Through porosity assessment of cements adjacent to HDG bars, it was found that hydrogen evolution accompanying zinc corrosion did not have an impact on the pore volume of cements: any additional pores created by hydrogen gas are filled by the zinc corrosion products. The negligible difference in pore volume between cements adjacent to chromated and non-chromated bars further confirmed that chromated treatment was unnecessary.

The major concern regarding the use of hot-dip galvanized (HDG) steel as reinforcement in concrete has been the high rate of corrosion experienced by the zinc during the first hours in the fresh, wet, and highly alkaline concrete. The present work was aimed at clarifying three issues associated with these concerns. The first involves the metallurgical phases at the surface of the zinc coating. The concentration of zinc at the surface is a function of processing procedures, surface treatment, and exposure to weathering. Differences in the coating surface composition influence the corrosion behaviour of HDG steel reinforcing bars when they are embedded in concrete. The second issue involves the increasing use of supplementary cementing materials in concrete, which change the chemistry of the concrete pore fluid, and also influence the corrosion. The third issue is that the initial corrosion is accompanied by hydrogen evolution, which could increase the pore volume of adjacent cement and thereby, decrease the bond stress between the concrete and the steel. In order to limit the hydrogen evolution, a chromate layer is applied after galvanizing. The results of the project have demonstrated that, during zinc corrosion in ordinary Portland cement (OPC) concrete, calcium hydroxyzincate formed on untreated HDG steel provided sufficient protection against corrosion. Therefore, it is concluded that treating HDG rebar with dilute chromic acid is unnecessary as a method of passivating zinc. A layer of zinc oxide and zinc carbonate formed through weathering on HDG bars slightly increased the initial corrosion rate and passivation time compared with the non-weathered rebars. HDG steel with an alloyed coating, i.e. consisting of Fe-Zn intermetallic phases, required a longer time to passivate than those with a pure zinc surface layer. The lower zinc content of the surface limited the rate of CHZ formation and, hence, delayed passivation. However, regardless of the surface condition, the coating depth loss after two days of embedment in OPC concrete was insignificant. In concretes containing 8% cement replacement with silica fume, or 25% cement replacement with slag, the initial corrosion rates were higher than those in OPC due to higher pH and lower calcium contents of the concrete pore solution. The higher corrosion rates lead to initial depth losses which are considered significant. However, in these concretes, chromate treatment was also shown to be unnecessary. Through porosity assessment of cements adjacent to HDG bars, it was found that hydrogen evolution accompanying zinc corrosion did not have an impact on the pore volume of cements: any additional pores created by hydrogen gas are filled by the zinc corrosion products. The negligible difference in pore volume between cements adjacent to chromated and non-chromated bars further confirmed that chromated treatment was unnecessary.

none