Analysis of the Corrosion Resistance of Bronze to Aluminium (ASTM B 824) in a Corrosive Environment Controlled with an Artificial Seawater Solution

This paper presents the analysis of corrosion resistance of bronzes to aluminum in a controlled corrosive environment. Three alloys were studied CuAl4.5; CuAl7,1 and CuAl10,1 (ASTM B824), whose chemical composition was evaluated by spectrometry (OES). To determine its metal phases, chemical attacks were carried out with FeCl3, HCl in 95% Ethanol and FeCl3, HCl, CrO3 in distilled water. The microstructures obtained were characterized by metallography using two microscopes, an optical and a scanning electron (SEM) and the phases obtained were compared. Subsequently, electrochemical corrosion tests were performed on each alloy. The electrolyte used in the tests was artificial seawater (ASTM D1141) with a pH of 10 ± 0.3. Then, the corrosion products were characterized by EDS and SEM. Once the identification phase was over, the products were removed with a 50% HCl solution. Corrosive attack damage in each microstructural matrix was identified and corrosion rates for each alloy were evaluated. Finally, the corrosion rate data were correlated with the Al and Sn percentages of the alloy. The results show that the higher the increase in aluminum, the lower the corrosion rate, for a maximum limit of Al = 10.11%; Sn = 0.13%; CR = 5,170 mpy; In addition, it was shown that these alloys are effective for marine environments with high salinity. The correlation can be used to estimate the corrosion rate for different pH of the electrolytic medium of any type of ferrous or non-ferrous alloy whose variables are dependent on its chemical composition. Keywords: corrosion, alloy, metallography, microstructure, spectrometry, electrochemistry. Resumen Este artículo presenta el análisis la resistencia a la corrosión de bronces al aluminio en un ambiente corrosivo controlado. Se estudiaron tres aleaciones CuAl4,5; CuAl7,1 y CuAl10,1 (ASTM B824), cuya composición química fue evaluada por espectrometría (OES). Para determinar sus fases metálicas se realizaron ataques químicos con FeCl3, HCl en Etanol al 95% y FeCl3, HCl, CrO3 en agua destilada. Las microestructuras obtenidas se caracterizaron mediante metalografía empleando dos microscopios, un óptico y un electrónico de barrido (SEM) y se compararon las fases obtenidas. Posteriormente, se realizaron ensayos de corrosión electroquímica a cada aleación. El electrolito utilizado en los ensayos fue agua de mar artificial (ASTM D1141) con un pH 10±0.3. Sucesivamente, se caracterizaron los productos de la corrosión mediante microscopia SEM. Una vez terminada la fase de identificación, se removieron los productos con una solución al 50% HCl. Los daños del ataque corrosivo en cada matriz microestructural fueron identificados y las tasas de corrosión para cada aleación fueron evaluadas. Finalmente, se correlacionaron los datos de tasas de corrosión con los porcentajes de Al y Sn de la aleación. Los resultados muestran que a mayor aumento de aluminio existe una menor tasa de corrosión, para un límite máximo de Al=10,11%; Sn=0.13%; CR=5,170 mpy; además, se demostró que estas aleaciones son eficaces para ambientes marinos con alta salinidad. La correlación puede ser utilizada para estimar la tasa de corrosión para diferentes pH del medio electrolítico de cualquier tipo de aleación ferrosa o no ferrosa cuyas variables sean dependientes de su composición química. Palabras claves: corrosión, aleación, metalografía, microestructura, espectrometría, electroquímica.

Proposed Alternative Rules for Establishing Pressure-Temperature Rating of Aluminum Alloy Flanges

Pressure-temperature ratings for aluminum alloy flanges made from ASTM B247 3003-H112 and 6061-T6 materials are covered in ASME B31.3 Appendix L since 1995. They were previously included in ANSI B16.5 between 1960 and 1968, and in ANSI B16.31 Non-ferrous Alloy Flanges from 1968 and until it was withdrawn in 1981. In 2018, Xu and Rana [PVP 2018-84076] used a modified version of the rules for establishing the pressure-temperature rating from ASME B16.5 Steel Flanges to re-assess the pressure-temperature rating of aluminum alloy currently listed in ASME B31.3 Appendix L. Based on their work, they recommended raising the pressure-temperature ratings for Classes 150, 300 and 600, as well as expanding rating to cover Classes 900 and 1500. In this paper, the author will revisit this topic, explain the background of why ANSI B16.31 was withdrawn and the drawbacks of higher pressure-temperature rating of aluminum alloy flanges. The author will also explain the concept of “ceiling pressure” used in B16 standards to cap the maximum pressure rating for flanges and valves, and significant difference in the modulus of elasticity between Carbon Steel and Aluminum alloys, and its impact on flange rigidity and leak tightness, and will propose alternative rules for establishing the pressure-temperature ratings for aluminum alloy flanges.

Retained Free Energy with Enhanced Nucleation during Electrostatic Levitation of Undercooled Fe-Co Alloys

Double recalescence in many ferrous alloy systems involves rapid solidification of metastable ferrite from the undercooled melt with subsequent transformation to stable austenite. Containerless processing is used to monitor the process using pyrometry and high-speed cinematography such that delay behavior can be predicted based on the application of the retained damage model (RDM). When comparing Fe-Cr-Ni alloys to Fe-Co alloys, the cluster attachment rate is enhanced while free energy retention is reduced. These trends are tied to specific alloy properties. A retained free energy criterion is proposed based on the ratio of thermophysical properties used to define the transformation driving force such that the thermodynamic limit for energy retention may be predicted. Surprisingly, at long delay times, healing occurs such that much of the retained free energy is not available to enhance the transition from metastable to stable phases. At delay times less than one second, no healing is observed and the RDM correctly predicts transformation delay behavior over a wide range of alloy compositions.

Studying a 2 millennia old bronze kettle using easily accessible characterization techniques

A bronze kettle dating from the 1st to 2nd century was found in a riverbed of the Kupa river in Croatia. After excavation it spent another 50 years in a depot of a museum in atmospheric conditions prior to starting the conservation treatment and our studies. A study on the surface layers development was performed to determine the whereabouts of the object through its history. This study is a demonstration of how such analysis can be used to reconstruct what the object went through during its life span. Samples taken from the kettle were observed by optical and scanning electron microscopy (SEM), and analysed by X-ray fluorescence (XRF), X-ray energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR).It was determined that the kettle is made of low-tin bronze, with low amounts of iron, aluminium, calcium and nickel. While being in the riverbed malachite formed on the kettle. After longer exposure to the river Si-oxides and CaCO3 formed on the surface of the kettle, over malachite. It was shown that the kettle probably had a ferrous alloy handle which degraded and disappeared in time. After excavation, the kettle came again in an oxygen-enriched atmosphere and formed new surface layers over the malachite layer. As the museum the kettle has been kept in since excavation is set in a highly industrial area sulphur compounds have been formed on the surface.

Transfer of rare earth to alloy and inclusion during slag-metal reaction

Rare earth metal transfer from slag to alloy and inclusion was investigated by slag-metal reaction method. Rare earth oxide (CeO2) employed in the refining slags was used a sample case. The results show that direct application of rare earth oxide in the slag is an alternative to traditional way which uses pure rare earth metal or rare-earth ferrous alloy to add rare earth in an alloy. Slag-metal reaction method proves to be an effective way to improve the rare earth transfer from slags to alloys with high content of Al. The content of Ce in the alloy increased with the increasing CeO2/Al2O3 mass ratio of the slag. As the Ce concentration of molten alloy increased from 0 to 105 ppm, the Al2O3 type inclusion was changed into cerium oxide, cerium sulfide and cerium oxy-sulfide inclusions. In addition, the morphology of inclusions was transformed from irregular to near spherical. Finally, the mechanism was discussed by thermodynamic analysis.

Development of the composition of a lubricant for injection under pressure with high sedimentation stability

The article describes the requirements for the lubricant used in injection molding of non-ferrous alloys. A methodology for conducting research to determine the sedimentation stability of a prepared lubricant is presented, as well as the results of a study of the sedimentation stability of a lubricant used in non-ferrous alloy die casting. It was established that in order to significantly increase the sedimentation stability of the compositions of lubricants for casting silumin based on the selected components, it is necessary to pre-heat the initial components to a temperature of at least 80 °C and mix them at a rotational speed of the dispersant blades of at least 6000 min–1. The optimal mode of lubrication with high sedimentation stability (more than 200 days) is observed at the following temperature and time indicators: the temperature of the heating of the starting components is at least 90 °C, the mixing time is 5 minutes, and the mixing frequency is 18000 min–1.

Using characterization techniques for determining the history of a 2 millennia old kettle made of bronze alloyed with iron

A bronze kettle dating from the 1st to 2nd Century was found in a riverbed of the Kupa river in Croatia. After excavation it spent another 50 years in a depot of a museum in atmospheric conditions prior to starting the conservation treatment and our studies. A study on the surface layers development was performed to determine the history of the object. This study is a demonstration of how such analysis can be used to reconstruct what the object went through during its life span.It was determined that the kettle is made of low-tin bronze, called mild bronze, with addition of iron, aluminum, calcium and nickel. Using iron for alloying copper is unusual since pure iron is generally not added to bronze, thus the presented case is a rare subject. Presence of cassiterite SnO2 showed that the kettle was used for preparing food on open fire prior to ending up in the river. While being in the riverbed malachite formed on the kettle. After longer exposure to the river Si-oxides and CaCO3 formed on the surface of the kettle, over malachite. It was shown that the kettle probably had a ferrous alloy handle which degraded and disappeared in time. After excavation, the kettle came again in an oxygen-enriched atmosphere and developed additional surface layers over the malachite layer.

Contactless Ultrasonic Treatment in Direct Chill Casting

Uniformity of composition and grain refinement are desirable traits in the direct chill (DC) casting of non-ferrous alloy ingots. Ultrasonic treatment is a proven method for achieving grain refinement, with uniformity of composition achieved by additional melt stirring. The immersed sonotrode technique has been employed for this purpose to treat alloys both within the launder prior to DC casting and directly in the sump. In both cases, mixing is weak, relying on buoyancy-driven flow or in the latter case on acoustic streaming. In this work, we consider an alternative electromagnetic technique used directly in the caster, inducing ultrasonic vibrations coupled to strong melt stirring. This ‘contactless sonotrode’ technique relies on a kilohertz-frequency induction coil lowered towards the melt, with the frequency tuned to reach acoustic resonance within the melt pool. The technique developed with a combination of numerical models and physical experiments has been successfully used in batch to refine the microstructure and to degas aluminum in a crucible. In this work, we extend the numerical model, coupling electromagnetics, fluid flow, gas cavitation, heat transfer, and solidification to examine the feasibility of use in the DC process. Simulations show that a consistent resonant mode is obtainable within a vigorously mixed melt pool, with high-pressure regions at the Blake threshold required for cavitation localized to the liquidus temperature. It is assumed that extreme conditions in the mushy zone due to cavitation would promote dendrite fragmentation and coupled with strong stirring, would lead to fine equiaxed grains.