How to Maintain a Stable Solution Chemistry when Simulating CO₂ Corrosion in a Small Volume Laboratory System
In laboratory experiments, corrosion of mild steel specimen in glass cells or autoclaves with a relatively small internal volume (of the order of 1 liter or less), will usually lead to a change in solution chemistry, (i.e., increase in ferrous ion concentration and solution pH) which will affect the corrosion product formation and ultimately the corrosion rate. However, in much larger field systems that are being simulated in the laboratory, such as for example oil and gas mild steel pipelines, the solution chemistry at any specific location does not change significantly over the same time period, since it is governed by the flow coming from further upstream. Therefore, it is very important to be able to maintain a stable solution chemistry in small scale laboratory experiments, in order to get a better simulation of corrosion seen in the field. In this work, a stable solution chemistry system was developed using ion exchange resins. H-form and K-form exchange resins were successfully tested in long term experiments aiming to keep pH and ferrous ion concentration reasonably stable. The results show that pH can be controlled within 0.02 pH units and ferrous ion concentration within 3 ppm. The results of electrochemical measurements and surface analysis show that there is a significant difference in both corrosion rate and corrosion product layer formation when a stable solution chemistry system is used.
Mechanistic Study of the Effect of Iron Sulfide Layers on Hydrogen Sulfide Corrosion of Carbon Steel
A novel experimental set-up was designed and built to investigate the effect of iron sulfide layer growth on H2S corrosion of carbon steel. Tests were conducted by purging 10% H2S/N2 into 1 wt.% NaCl solution at different temperature (25 °C-80 °C), different pH (pH 4 to pH 6) and different flow conditions (60 rpm and 600 rpm magnetic stirring rates). The exposure period was from 1 day to 7 days. The corrosion behavior was monitored by linear polarization resistance (LPR) and checked with weight loss analysis. The morphology and compositions of surface corrosion products were analyzed by Scanning Electron Microscopy (SEM/EDS), cross section analysis and X-ray Diffraction (XRD) methodology. The results show the balance between iron sulfide precipitation and undermining process, characterized by the scaling tendency, can lead to a variety of corrosion outcomes depending on the environmental parameters such as temperature, pH, and flow rate. Protective corrosion product layer and low corrosion rate were observed at high pH, temperature and low flow rate due to precipitation of a dense corrosion product layer.
Effects of Racial Diversity on Complex Thinking in College Students
Are experiment varying the racial (Black, White) and opinion composition in small-group discussions was conducted with college students (N = 357) at three universities to test for effects on the perceived novelty of group members' contributions to discussion and on participants' integrative complexity. Results showed that racial and opinion minorities were both perceived as contributing to novelty. Generally positive effects on integrative complexity were found when the groups had racial-and opinion-minority members and when members reported having racially diverse friends and classmates. The findings are discussed in the context of social psychological theories of minority influence and social policy implications for affirmative action. The research supports claims about the educational significance of race in higher education, as well as the complexity of the interaction of racial diversity with contextual and individual factors.