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ABSTRACT Extracts of tobacco plants show considerable promise as environmentally acceptable corrosion inhibi- tors. Use of extracts obtained from stems and twigs, as well as leaves, show significant corrosion inhibi- tion during immersion of aluminum or steel in saline solutions and immersion of steel in strong pickling acids. In several cases, the inhibition is greater than that provided by chromates and is provided over a wide range of extract solution concentrations. When steel was treated in sulfuric acid with tobacco ex- tract to remove mill scale and rust, the steel emerged bright and shiny. When treated in sulfuric acid alone, the steel was blackened and pitted. The tobacco extracts provide corrosion protection from a re- newable resource with little or no environmental impact. The use of waste plant material enables an in- expensive source of corrosion inhibitors. INTRODUCTION There is a continual need to develop environmentally friendly corrosion inhibitors to replace the tradi- tional inorganic corrosion inhibitors, such as chromates and lead, which have significant health, safety, and environmental concerns. Both are listed as persistent, bioaccumulative, and toxic (PBT) chemicals] Because PBT chemicals do not readily break down or decrease in potency in the environment, they ac- cumulate and have greater potential to cause long-term human health or ecological problems. They con- tinue to be an environmental concern long after they are used and the nation's goal is to reduce the gen- eration of these chemicals in hazardous waste by 50% by 2005 with source reduction and recycling, as intended by the Resource Conservation and Recovery Act (RCRA), Clean Air Acts, the Pollution Pre- vention Act, and the Hazardous and Solid Waste Amendments (HSWA), among others. Thus, new, ef- fective inhibitors that are safe and environmentally benign must be found. Extracts from tobacco plants show excellent corrosion inhibition properties for several metals. 2"4 The tobacco plant is a virtual chemical factory with over 4,000 compounds being reported by the USDA. Tobacco is currently being evaluated as a production system for antibiotics, sugars, industrial enzymes, and anti-cancer and AIDS compounds. 59 Some of the tobacco constituents show remarkable corrosion inhibitive properties. Tobacco extracts represent a major new initiative in the corrosion inhibition mar- ket with the following potential advantages: ? Low cost and high effectiveness ? Environmentally acceptable ? Low toxicity ? Readily available and renewable. At the beginning of the twentieth century and earlier, biomass, in the form of wood, was the major source of organic chemicals in the US. It is projected that in the coming years, biomass will again come to be viewed as an important, renewable feedstock for the wide range of needed chemicals. Biomass has a potential advantage over petrochemical feedstocks: it already contains a wide range of naturally- synthesized chemical compounds that can be extracted by straightforward processes, obviating the need for complex manufacturing syntheses from basic, petroleum-derived, building blocks. Tobacco should be viewed as an incredibly rich source of complex chemicals. Extraction of chemicals from biomass is a more attractive approach than merely using biomass to make fuels as the latter destroys these complex molecules. Corrosion inhibitors have been studied for many years [see, e.g., Ref. 10 and 11]. Many types of or- ganic compounds have been found to act as inhibitors [see, e.g., Ref. 12 and 13], but most of these com- pounds have remained as laboratory data. One reason seems to have been that the cost of manufacture of these compounds is generally to
- Water & Waste Management > Water Management > Water & Sanitation Products (1.00)
- Materials > Chemicals > Specialty Chemicals (1.00)
- Materials > Chemicals > Commodity Chemicals (1.00)
- Government > Regional Government > North America Government > United States Government (1.00)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Health, Safety, Environment & Sustainability > Environment (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
ABSTRACT Electrochemical Impedance Spectroscopy (EIS) is an accepted laboratory technique for evaluating coatings in an electrolyte. Recently, sensors have been developed which allow EIS to be taken on surfaces in any orientation and without foreign electrolyte, consequently allowing a coated metal surface to be measured in-situ. These sensors have been demonstrated in the laboratory to acquire spectra equivalent to the traditional technique, and add the advantage that coatings may be examined while still in test environments such as constant humidity or salt fog. With the addition of a field-ready portable potentiostat, these sensors can become valuable tools for coatings inspection in the field. A sensor may be permanently mounted to a structure, or may be pressed against a surface only for the duration of a measurement. The sensor results allow ready evaluation of the moisture content of a coating, consequently providing an early warning of impending substrate dam- age before serious under-coating corrosion has an opportunity to begin. INTRODUCTION Field and/or depot-level inspection of the many painted metal surfaces that comprise both stationary structures and vehicles is a typical part of maintenance programs. Such inspections are frequently based on elapsed time schedules, which are often developed from historical data on time-to-failure. Evaluation tools that would allow a transition to a condition-based maintenance program would in many cases re- duce the frequency of inspections. The labor, waste management, and replacement materials requirements of some inspection methods, particularly those that require disassembly to inspect hidden areas and/or stripping of complete coating systems to inspect the underlying substrate for corrosion, may also be minimized. Reducing the labor, waste stream, and materials needed for individual inspections, as well as the frequency of inspections overall, will result in substantial savings in the maintenance of vehicles such as aircraft and marine vessels, and infrastructure such as bridges and piers. Electrochemical Impedance Spectroscopy (EIS) is an established laboratory technique that has been used to study the corrosion of bare and coated metal surfaces while immersed in an electrolyte. 1-10 It involves the application of a small AC voltage to a metal substrate. The frequency of the AC voltage is varied and the resulting impedance spectrum is recorded. AC techniques have an advantage over DC potential corrosion monitoring techniques in that the use of very small voltage perturbations in the AC techniques allow observation of corrosion reactions occurring in essentially equilibrium conditions. Traditionally, the surface to be examined is exposed to an electrolyte in a corrosion cell that also contains a reference and a counter electrode. Samples may be inserted into immersion cells, or specially designed cells may be clamped onto the sample surface and sealed with a gasket. Although the EIS technique causes little external perturbation to the system under study due to the small applied voltage, the immersion requirement frequently does not represent the intended in-situ environment of a coating in use. Excess water absorption and possible interaction with electrolyte constituents may cause artifactual damage, l~ leading to results that deviate from the true performance of coatings in the field. In addition, the use of electrolytes and clamp-on cells limits the usefulness of the technique in monitoring working structures, which frequently have surfaces that are non-horizontal, curved, and sometimes hidden or otherwise inaccessible. Other systems make use of liquid or gel-type electrolytes in spongy materials, which increases
- Transportation > Ground > Road (0.47)
- Transportation > Passenger (0.46)
- Water & Waste Management > Water Management (0.34)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)