A critical aspect of the field of corrosion research is that of corrosion under conditions of turbulent flow. †This is an area that is commonly known in the literature as flow accelerated corrosion (FAC). It has been studied in a number of applications such as the nuclear industry oil pipelines household plumbing devices and maritime components to mention but a few. There is only poor if any quantitative information concerning the degree of turbulence for most FAC studies. Corrosion studies performed in the laboratory use either stirred fluids jet impingement or rotating disks to achieve low levels of turbulence. There are only a few studies designed to correlate the results from these tests. The difficulty of obtaining good quantitative measures of the turbulence of the fluid explains the lack of quantitative correlations of FAC and the fluid flow.This paper describes a unique apparatus known as the Virginia Tech High Turbulence Corrosion Loop (VTHTCL) in which the study of the temperature dependence of corrosion in highly turbulent aqueous solutions at Reynolds numbers (Re) between approximately 15000 and 1000000 can be performed. Great care has been taken to assure that Re can be quantified to an accuracy of better than 5% and a precision of better than 2%. Studies of 1100 Al were conducted in a simulated Light Water Reactor (LWR) coolantwhich was used to prove the experimental concept (see paper by Carney and Hendricks this session). These measurements will for the first time allow a quantitative correlation of the degree of turbulence in the fluid with the mechanisms and kinetics of erosion-corrosion. By performing the studies in a corrosion loop of sufficient length it is assured that the turbulence of the fluid at the sample positions will be fully developed thus allowing scaling of the results from laboratory results to industrial-scale applications.The HTCL comprises a 5 HP motor driving a 6-blade impeller that can pump fluid through the system at up to 200 gpm. Fluid is stored in a 10 gal. tank fitted with a 3 kW heating element. Fluid is drawn from the tank and pumped up to a 18 ft long loop that contains instrumentation for control and measurement of the flowing fluid. †The pipe is schedule 80 CPVC which was chosen for its broad corrosion resistance low cost wide operating temperature bounds and ease of construction without specialized equipment. †The turbulence of the fluid in the tank assures that the fluid is saturated with oxygen at all times. Instrumentation includes a calibrated turbine flow meter a conductivity meter and ports for two commercial sample probes manufactured by Metal Samples Inc. Water is then returned to the tank. There is a PRT and a level detect sensor in the storage tank ; the former is used to control the temperature of the fluid and the latter to assure safety in the case of a loss of coolant (LOC) accident. There is a redundant thermocouple mounted on the exterior of the tank that is used as a safety limit in the event of runaway overheating of the fluid. The control panel includes a variable frequency drive (VFD) that controls the fluid flow the control displays for the flow meter and the conductivity meter the PID temperature controller and a variety of control switches and displays used to assure maximum safety of the system.A series of experiments was run to calibrate the system. The degree of heating caused by friction of the fluid introduced by the impeller ranged from 2.5 C at 21 gpmto 67 C at 96 gpm. This heating limited the range of volumetric fluid flow that could be used at any given temperature.Fluid turbulence has been quantitatively described over a half a century ago. Recent developments in hot-wire anemometers and in-situ shear stress sensors now allow the quantification of turbulence in three dimensions. These capabilities have heretofore not been applied to the study of erosion-corrosion. Nesic and Postwaite (1990) report an early study of turbulence and erosion-corrosion but their work did not quantify the turbulence. Wood et. al. (2002) have studied erosion-corrosion using electrochemical measurements. However these measurements only look at the corrosion and do not correlate it with the fluid flow. Of thevarious statistical parameters that define the degree of turbulence the shear stress at the wall of the tube is of critical importance for studies of the corrosion of the pipe. It is an objective of our research to measure the degree of erosion-corrosion and the statistical parameteers ofthe fluid flow.Experiments to study the corrosion of 1100 Al in turbulent deionized water-boric acid-lithium hydroxide solutions that have the same composition as the coolant of light water reactors have been made at 80C where unusual corrosion and material erosion have been observed.Two separate tests were conducted each under different flow conditions. The specimens were mounted incorrosion probes of linear polarization resistance (LPR) and electrical resistance (ER)provided by Metal Samples Inc. These were then installed into the corrosion loop. The aqueous solution of B(OH)3and LiOH was added into the mixing tank where it was heated to 80 Centigrade. The experiments ran for 72 hours at flow conditions of35 and 59 gpm. Data loggers were connected to the probes and recorded the corrosion at intervals of one hour.The LPR data for the 35 gpmtest showed an exponentially decaying corrosion rate with time. This corrosion behavior and diffusion kinetics suggests the formation of an oxide layer. The 59 gpmtest showed a relatively constantcorrosion rate over the time period. To elucidate the mechanism of corrosion (either erosion of oxide or decreased growth rate of oxide) we will change the operating temperature and thus the dissolved oxygen concentration and adjust the flow rate to assure constant Re. Samples of the LPR probes were examined using optical microscopy scanning electron microscopy and energydispersive x-rayspectroscopyin order to determine oxide film thicknesses and composition. An unusual periodic variation in the composition of the oxide film was observed with localized Al and Fe rich regions. Further localized erosion and substrate removal was observed on the downstream side.Based on the first experimental results a number of modifications of the instrument must be made for continued research. These include: incorporating a heat exchanger to reduce/eliminate the heat added by the impeller that pumps water through the system thus allowing measurements at room temperature over the full range of fluid flows; increasing the number and variety of sensors used to measure the fluid chemistry such as dissolved oxygen pH and electrical conductivity sensors and thermocouples to monitor sample temperatures thus providing better information necessary for understanding the electrochemistry of the corrosion/erosion processes; the design and construction of shear stress sensors that will be installed in the walls of the pipe opposite corrosion samples that will allow for the first time in corrosion research the determination of the shear stresses at the wall of piping during turbulent flow and their effect on the corrosion process; and the development of a data logger that will allow for automatic recording of the data from the corrosion sensors the water chemistry sensors and the fluid flow control parameters. These modifications to HTCL will greatly increase the range of materials and corrosion processes that can be studied.As both a materials science and a materials engineering department the faculty and students in the MSE Department at Virginia Tech are interested in both the science of such corrosion problems and in the practical engineering applications of the science to the solution of industrial problems. We see the VTHTCL as an ideal vehicle by which such a philosophy may be taught while at the same time educating new members of NACE as the next generation of corrosion engineers.

Key words: Flow Related Materials Degradation, FRMD, Turbulence, Corrosion Loop, Pipe Corrosion, Erosion Corrosion, UNS A91100 aluminum, Shear Strain Gauge, Bed Shear