Passivation treatment

Degreasing may be necessary, especially on new plant. For optimum boiler life, passivation treatment is recommended. 

Zinc will initially react with cement-based materials with the evolution of hydrogen. This reaction can be controlled by the presence of soluble chromate either in the cement (over 70 ppm) or as a chromate passivation treatment to the zinc surface. Zinc can therefore be used to provide additional protection to steel in concrete. It is more effective in cmbonated concrete than in chloride-contaminated concrete. 

BS 6536 1985 refers to four grades of carbon steel strip coated with Al-Si alloys containing 5-11 wt.% Si. The availability of the steel grades allows account to be taken of the type and degree of forming which is to be applied to the coated steel. Various coating masses are supplied in the range 40-180 g/m which may be additionally protected by a chromate passivation treatment. 

Next, the boiler must be passivated. The boiler is filled above normal working level and ammonia/hydrazine or a similar passivation treatment is added. The boiler is first given a hydrostatic test. Following this, the water level is dropped, and the boiler is lightly fired for 4 to 6 hours to ensure adequate passivation of the boiler surfaces. 

Conference, West Virginia University. Neculita, C-M, Zagury, G, Bussiere, Bruno 2007. Passive Treatment of Acid Mine Drainage in Bioreactors, using Sulphate Reducing Bacteria Critical Review and Research Needs. Journal of Environmental Quality, 36, 1-16... 

Hedin, S. Watzlaf, G., Narin, R. 1994. Passive treatment of acid mine drainage with limestone. Journal of Environmental Quality, 23, 1338-1345. 

A further advantage of installing a pilot wetland was the provision of an experimental basis for passive treatment systems which could be used at other sites within the WISMUT project. 

Constrncted wetlands are a passive treatment system. Therefore, operation and maintenance costs are very low compared to that of active treatment processes (D10500Q, p. 1). Construction costs vary considerably from site to site. Constrncted wetlands may be not be financially viable at all sites (D20499J, p. 2). 

Constmcted wetlands use biological processes inherent in natnral wetlands and a system designed to optimize those processes to treat wastewater contaminants specific to a particnlar site. Constructed wetlands are passive treatment systems that mimic, rather than overcome, natnral processes. Consequently, the cost of operation and maintenance is significantly lower than for... 

Unit cost values for excavation, geomembranes, or clay cell liners and other construction costs are identical for both anaerobic and aerobic passive-treatment systems. 

The vendor states that savings associated with the EnviroMetal Process are due to the low operation and maintenance costs for treatment walls. Because contaminants are destroyed rather than removed, process monitoring costs are negligible, and little or no waste products require disposal or regeneration on a regular basis. The vendor also states that since the technology is a passive treatment, there is no need for manual labor to operate, monitor, and maintain the system (D14522C, pp. 19, 20). 

Reclaim is a passive, in situ technology that uses a hydrophobic porous polymer to attract, adsorb, and concentrate petroleum hydrocarbons and volatile organic compounds (VOCs) from soils and/or groundwater. Reclaim is considered a passive treatment technology because it requires no mechanical equipment remediation consists of placing polymer-filled canisters in recovery wells and allowing the containers to attract and adsorb organic contaminants. Reclaim canisters are then recycled and contaminants recovered for analysis and/or disposal. This polymer extracts contaminants whether they are in liquid phase, vapor phase or dissolved phase in water. 

Metals removal via peat is an in situ, passive treatment technology being developed to treat groundwater contaminated with heavy metals and radionnclides. Bench-scale tests indicate that peat may be an inexpensive and effective material for trapping metals. 

Because ORC is a passive treatment technology, it is virtually maintenance free. There are no mechanical components to maintain, and, once installed, the compound needs to be replaced only once every 4 to 6 months. Treatment costs of remediating a source area may be reduced by placing ORC in wells downgradient from the source. In some cases, ORC can be placed in existing wells, further reducing costs. 

Nuttall, C. A. 2003. Testing and performance of a newly constructed full-scale passive treatment system at Whittle Colliery, Northumberland. Land Contamination and Reclamation, 11,... 

Younger, P. L., Jayaweera, A. et al. 2003. Passive treatment of acidic mine waters in subsurface-flow systems exploring RAPS and permeable reactive barriers. Land Contamination and Reclamation, 11, 127-135. 

The particles continue to fly into the sampling chamber through an orifice between the reaction and the sampling chamber. The pressure of the sampling chamber is 9.5 X 10-4 torr. The particles are collected in a form that is convenient for characterization or application. For example, the particles are collected on a microgrid for transmission electron microscope (TEM) observation and on a polyimid-film for MOssbauer and x-ray diffraction studies. A standard passivation treatment, namely, slow introduction of O2 gas followed by the introduction of dry air to the chamber, is made. 

In many studies the chemisorption and the surface reaction is just the first step in a series of solid state reactions that take place as atoms from the surface move into the bulk. Corrosion, oxide, carbide and other compound formations are generally initiated at the surface and then propagate into the bulk. There may be a concentration gradient of certain constituents at the surface in a multicomponent system that would influence the mechanical or chemical properties of the system. Hardening of materials and other forms of passivation treatment frequently involve introduction of certain substances only in the near surface region. For the investigation of these problems RHEED is a powerful technique. 

Morrison SJ, Metzler DR, Dwyer BP. Removal of As, Mn, Mo, Se, U, V and Zn from groundwater by zero-valent iron in a passive treatment cell reaction progress modeling. J Contam Hydrol 2002 56(1 2) 99—116. 

Wallinder et al. examined passivation of 316L using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and x-ray photoelectron spectroscopy (XPS) techniques to examine the relationships between corrosion resistance and surface chemistry after passivation treatments (17). The... 

Hong et al. examined the effect of nitric acid passivation on type 430 ferritic stainless steel using potentiodynamic polarization, EIS, and Auger electron spectroscopy (AES) (18). Passivation treatments were carried out on wet polished surfaces by immersion for 60 minutes in nitric acid solutions ranging from 1 to 61% at 50°C. Pitting potential and the magnitude of the total impedance were positively correlated with surface Cr concentration. In response to this study,... 

Naim, R. W., R. S. Hedin, and G. R. Watzlaf. 1991. A preliminary review of the use of anoxic limestone drains in the passive treatment of acid mine drainage. In Proceedings of the 12th Annual West Virginia Surface Mine Drainage Task Force Symposium. Morgantown, WV, pp. 23-38. 

The remaining spectra in Figure 6 show evidence of similar formation of SiO for the different passivation treatments. The extent of oxide formation as judged from the intensity of the peak at 1070 cm" depended on the particular passivation treatment as did stability to an additional 10 min. "standard" RIE. For example, SME resulted in a much greater extent of oxide formation (curve 2d) than high-bias (curves 3d and 4d) or barrel etching (curve 5d). 

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