Sub-surface corrosion research on rock bolt system, perforated SS sheets and steel sets for Yucca Mountain Repository
Friction type steel rock bolts are one of the most commonly used for reinforcing tunnels, since the late 1970’s due to their ability to sustain large rock mass displacements. These ASTM A607 steel rock bolts are tubes slotted along the length with one end tapered for easy insertion into a drill hole and the other end with a welded ring flange to hold the bearing plate. It is more commonly used these days to reinforce tunnels, and also being studied for underground support for nuclear repositories. We studied corrosion behavior of this A607 steel rock bolts using electrolytes in three different concentrations; 1X,10X,100X, in aerated (oxygenated) and deaerated (nitrogenated) conditions from 298 to 363K for nuclear repository applications. The corrosion behavior for 1X and 10X concentrations for this rock bolt were similar in both aerated and deaerated conditions except the corrosion rates were a order of magnitude higher in the aerated condition; ranging from ~30 to 200mm/yr for deaerated and 150 to 1600 mm/yr for aerated. The corrosion behavior using 100X electrolyte was quite different in aerated condition showing initial increases in the corrosion rate between 298 to 338K ( ~210 to 2400 μm/yr) and an unusual steep decrease from 338 to 348K(~2400 to 750 μm/yr). General as well as pitting corrosion were observed for these steels. In this paper we report results from potentiodynamic polarization and potentiostatic tests in simulated electrolytes as a function of concentration, temperature and environment. We also compare corrosion behavior of the A607 rock bolt steel with 1040 and A36 steels using the same electrolyte and similar environment.
Electrochemical, Thermodynamic, Surface, and Spectroscopic Study in Inhibition of Iron Corrosion with Turmeric Root Extract (TRE)
Turmeric root extract was tested as corrosion inhibitor for iron in 0.5 M HCl, using potentiodynamic polarization and electrochemical impedance spectroscopy, scanning electron microscope, and energy dispersive X-ray analysis. The inhibition efficiency increases as the time of immersion rises but decreases with temperature rise. The Nyquist plots showed that the charge transfer resistance increases and the double-layer capacitance decreases as the time of immersion increases. Tafel results show that both corrosion current and corrosion speed are reduced with time of immersion. All impedance spectra of EIS tests exhibit one capacitive loop, which indicates that the corrosion reaction is controlled by charge transfer process. Inhibition efficiency increases with the concentration of the inhibitor reaching its maximum value, 88.90%, at 8 g/100 mL. Thermodynamic parameters, Ea, ∆H*, and ∆S*, were estimated, and the mechanism of corrosion and inhibition was discussed. The adsorption of turmeric root extract followed Langmuir adsorption isotherm.
Trends in kiln drives
The heart of the cement plant is the rotary kiln, and continuous quality production of cement clinker depends on the continuous accurate performance of the rotary kiln drive.