Corrosion Activity of Stainless Steel SS430 and Carbon Steel B450C in a Sodium Silicate Modified Limestone-Portland Cement Extract

Stainless steel SS430 and carbon steel B450C were exposed for 30 days to the aqueous extract of sodium silicate-modified limestone-Portland cement as an alternative for the partial replacement of the Portland cement clinker. The initial pH of 12.60 was lowered and maintained at an average of 9.60, associated with air CO₂ dissolution and acidification. As a result, the carbon steel lost its passive state, and the corrosion potential (OCP) reached a negative value of up to 296 mV, forming the corrosion layer of FeO, and FeOOH. In the meaning time, on the stainless steel SS430 surface, a passive layer of Cr₂O₃ grew in the presence of FeO, Fe₂O₃ and Cr(OH)₃ corrosion products; thus, the OCP shifted to more positive values of +150 mV. It is suggested that a self-repassivation process took place on the SS430 surface due to the accumulation of alkaline sulfates on the interface. Because of the chloride attack, SS430 presented isolated pits, while on B450C, their area was extended. The quantitative analysis of EIS Nyquist and Bode diagrams revealed that the Rp of the corrosion process for SS430 was 2500 kΩcm², ≈32 times lower in magnitude than on B450C, for which the passive layer tended to disappear, while that on SS430 was ≈0.82 nm.

Corrosion Activity of Carbon Steel B450C and Stainless Steel SS430 Exposed to Extract Solution of a Supersulfated Cement

Carbon steel B450C and low-chromium stainless steel SS430 were exposed for 30 days to supersulfated "SS1" cement extract solution, considered as a "green" alternative for partial replacement of the Portland cement clinker. The initial pH of 12.38 dropped since the first day to 7.84, accompanied by a displacement to more negative values of the free corrosion potential (OCP) of the carbon steel up to ≈-480.74 mV, giving the formation of γ-FeOOH, α-FeOOH and Fe₂O₃, as suggested by XRD and XPS analysis. In the meantime, the OCP of the SS430 tended towards more positive values (+182.50 mV), although at lower pH, and XPS analysis revealed the presence of Cr(OH)₃ and FeO as corrosion products, as well the crystals of CaCO₃, NaCl and KCl. On both surfaces, a localized corrosion attack was observed in the vicinity of local cathodes (Cu, Mn-carbides, Cr-nitrides, among others), influenced by the presence of Cl^- ions in the "SS1" extract solution, originating from the pumice. Two equivalent circuits were proposed for the quantitative analysis of EIS Nyquist and Bode diagrams, whose data were correlated with the OCP values and pH change in time of the "SS1" extract solution. The thickness of the corrosion layer formed on the SS430 surface was ≈0.8 nm, while that on the B450C layer was ≈0.3 nm.

143 COMPARISON OF COMMERCIAL IN VITRO EMBRYO PRODUCTION AND PREGNANCY RATES OF BRAHMAN DONORS IN PANAMA VERSUS DOMINICAN REPUBLIC

It has been previously demonstrated (IETS 2011) that Panama is applying the biotechnology of in vitro embryo production (IVP) to their bovine reproduction management systems. The present work demonstrates the ability to apply the IVP technology across 2 distant country borders. Herein, we demonstrate that a country (Dominican Republic; DR) that does not have a bovine IVP laboratory can take advantage of fresh bovine IVP embryos for transfer using distant IVP facilities in another country (Panama; ~1500 km away). The objective of this study was to demonstrate that a model system for large-scale commercial in vitro bovine embryo production for beef and dairy producers, that do not have IVP technology in their home country, could be developed producing comparable results. As the same laboratory provides IVP services to the both countries, a special sanitary protocol was developed in order to legalize the exchange of biological materials (oocytes or embryos). The data obtained in DR was compared to Panamanian client data because identical conditions were utilised for IVP. Cattle production systems were similar, as Brahman (a Zebu type of cattle) is the most popular breed in both countries. Oocytes were collected from 10 different herds in Panama and 4 different herds in DR. The oocytes were transported in an oocyte transporter in both instances. However, oocytes from DR were transported in InVitro Brasil™ maturation medium from 12 to 18 h and in Panama from 6 to 12 h before they were placed in a standard CO2 incubator. In both cases, the oocytes were matured for 24 h before fertilization with conventionally frozen Brahman semen in InVitro Brasil™ fertilization medium, followed by culture for up to 7 days in InVitro Brasil™ embryo culture medium. The embryos were transferred on Day 7, either in Panama or DR. They were transported by car in Panama and via airplane back to DR. A comparison of oocyte number and quality, cleavage, embryo production, and pregnancy rate, was made using the same in vitro production system for Brahman donors from September 2012 until May 2013. The difference between sites in the relative number of viable oocytes, relative number of cleaved oocytes among viable oocytes, relative number of embryos produced among cleaved oocytes, and relative number of embryos produced among viable oocytes was tested using Fisher's exact test. Pregnancy rate was analysed with chi-squared. We realise these results represent field data; however, we believe the present work is a significant step in demonstrating the potential for wide commercial-scale dissemination of IVP technology between distant countries. The number of embryos produced in Panama was slightly, but significantly, higher than those produced in DR; this is likely due to the larger number of donors and oocytes from the Panamanian herds. However, the pregnancy rate was higher in DR, likely due to the health status of DR recipients. These data illustrate that IVP using Brahman donors could be used as a tool to improve and spread superior genetics. Furthermore, this technique can serve as a model for other Central American and Caribbean countries under similar management systems. Table 1.Panama and the Dominican Republic in vitro Brahman embryo production and pregnancy (September 2012 through May 2013)