Corrosion of Titanium Alloys Anodized Using Electrochemical Techniques

The anodization of titanium has been an excellent option for protecting titanium and its alloys from corrosive environments such as acids and chloride systems, by generating a homogenous oxide layer. The objective of the current investigation was to evaluate the electrochemical corrosion behavior of alloys Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V anodized in 1MH2SO4 andH3PO4 solutions at a current density of 2.5   10–3 A/cm2. The anodization’s electrochemical characterization was achieved in NaCl and H2SO4 at 3.5% wt. electrolytes. Scanning electron microscopy (SEM) was employed to determine the anodized thickness and morphology. Cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy (EIS), based on ASTM G61-86 and G106-15 Standards, were the electrochemical techniques mainly employed. The anodized samples presented a change in Ecorr values and a higher passivation zone. The EIS plot showed a higher resistance for samples anodized in H3PO4 and Ti-6Al-2Sn-4Zr-2Mo

Carbonation Depth of Sustainable Concrete Made with Agroindustrial and Industrial Waste Exposed to the Urban Environment of the City of Xalapa, Ver; Mexico

In the present investigation the effect of the urban environment of the city of Xalapa, Ver., México in the depth carbonation in Sustainable Concrete made with Agro-Industrial and Industrial Waste Materials like Sugar Cane Bagasse Ash (SCBA) and Silica Fume (SF), was evaluated. The Sustainable Concretes and the Conventional Concrete (Concrete of reference) were designed for a relation water/cement= 0.65 according to the indicated for the ACI 211.1. The Conventional Concrete was elaborated with 100% of Portland cement, and the Sustainable Concretes with partial substitution of Portland cement for the waste of SCBA and SF in percentages of 10, 20, 30, 40, and 50%. The results through the application of phenolphthalein, indicate that the Carbonation depth is proportional to the increase of the substitution of Portland Cement for agro-industrial and industrial waste. The sustainable concrete with 50% of substitution of SCBA-SF presents the worst performance, with a carbonation depth of 1.48 cm, which represents an increment of more of 350% than the conventional concrete at being exposed for one year to the present environment of stud

Anticorrosive efficiency of the AISI 316 SS in sustainable ecological concrete manufactured with SCBA-SF exposed to magnesium sulphate

In this research, it was evaluated the anticorrosive efficiency of AISI 316 SS embedded in sustainable ecological concrete (SEC) manufactured with partial substitutions of portland cement by combinations of SCBA and SF in 10%, 20%, and 30%. For the electrochemical evaluation, the sustainable ecological concretes (SEC) were exposed to solution at 3.5% of MgSO4, these aggressive ions are found in soils, industrial or marine environments and that interact with the civil works that are built in these places. The dosage or proportioning of the sustainable ecological concrete (SEC) mixtures was carried out as indicated by ACI 211.1. The anticorrosive efficiency of the AISI 316 SS was evaluated through the tests of the potential of corrosion (Ecorr) and corrosion rate (Icorr) during a period of 180 days of exposition to the aggressive medium. The values of ecorr indicate in the AISI 316 SS a 10% of corrosion risk and uncertainty at the end of monitoring, according to the norm ASTM C-876-15, in all the mixtures, but the values of icorr in the specimens manufactured with SEC indicate resistance to sulfate corrosion more than 10 times compared to conventional concrete and AISI 1018 steel

Physical, Mechanical and Durability Properties of Ecofriendly Ternary Concrete Made with Sugar Cane Bagasse Ash and Silica Fume

In the present investigation, the physical, mechanical and durability properties of six concrete mixtures were evaluated, one of conventional concrete (CC) with 100% Portland cement (PC) and five mixtures of Ecofriendly Ternary Concrete (ETC) made with partial replacement of Portland Cement by combinations of sugar cane bagasse ash (SCBA) and silica fume (SF) at percentages of 10, 20, 30, 40 and 50%. The physical properties of slump, temperature, and unit weight were determined, as well as compressive strength, rebound number, and electrical resistivity as a durability parameter. All tests were carried out according to the ASTM and ONNCCE standards. The obtained results show that the physical properties of ETC concretes are very similar to those of conventional concrete, complying with the corresponding regulations. Compressive strength results of all ETC mixtures showed favorable performances, increasing with aging, presenting values similar to CC at 90 days and greater values at 180 days in the ETC-20 and ETC-30 mixtures. Electrical resistivity results indicated that the five ETC mixtures performed better than conventional concrete throughout the entire monitoring period, increasing in durability almost proportionally to the percentage of substitution of Portland cement by the SCBA–SF combination; the ETC mixture made with 40% replacement had the highest resistivity value, which represents the longest durability. The present electrical resistivity indicates that the durability of the five ETC concretes was greater than conventional concrete. The results show that it is feasible to use ETC, because it meets the standards of quality, mechanical resistance and durability, and offers a very significant and beneficial contribution to the environment due to the use of agro-industrial and industrial waste as partial substitutes up to 50% of CPC, which contributes to reduction in CO2 emissions due to the production of Portland cement, responsible for 8% of total emissions worldwide

Electrochemical Corrosion of Galvanized Steel in Binary Sustainable Concrete Made with Sugar Cane Bagasse Ash (SCBA) and Silica Fume (SF) Exposed to Sulfates

This research evaluates the behavior corrosion of galvanized steel (GS) and AISI 1018 carbon steel (CS) embedded in conventional concrete (CC) made with 100% CPC 30R and two binary sustainable concretes (BSC1 and BSC2) made with sugar cane bagasse ash (SCBA) and silica fume (SF), respectively, after 300 days of exposure to 3.5 wt.% MgSO4 solution as aggressive medium. Electrochemical techniques were applied to monitor corrosion potential (Ecorr) according to ASTM C-876-15 and linear polarization resistance (LPR) according to ASTM G59 for determining corrosion current density (icorr). Ecorr and icorr results indicate after more than 300 days of exposure to the sulfate environment (3.5 wt.% MgSO4 solution), that the CS specimens embedded in BSC1 and BSC2 presented greater protection against corrosion in 3.5 wt.% MgSO4 than the specimens embedded in CC. It was also shown that this protection against sulfates is significantly increased when using GS reinforcements. The results indicate a higher resistance to corrosion by exposure to 3.5 wt.% magnesium sulfate two times greater for BSC1 and BSC2 specimens reinforced with GS than the specimens embedding CS. In summary, the combination of binary sustainable concrete with galvanized steel improves durability and lifetime in service, in addition to reducing the environmental impact of the civil engineering structures