The paper will review recent literature concerning the use and application of corrosion and scale inhibitors for aqueous fluids that fit into the "green" category through reduced health, safety, or environmental risk. The types of corrosion inhibitors reviewed include those developed for use in oilfield acidizing fluids or chemical cleaning formulations, downhole treating applications, pure water, and scale inhibitors in brines. Examples of the development of several green formulations also will be described.
Green, or low toxicity formulations have become the goal of most inhibitor developers; however, there is not total agreement[l] on the definition of "Green" chemistry. Darling of the United States Environmental Protection Agency (EPA) defines this term as "pollution prevention at the molecular level, designed to reduce or eliminate the use or generation of chemicals that are hazardous to human health or the environment." A major oil service company described a procedure for quantitative assessment of health, safety, and environmental (HSE) impacts of prospective new chemicals (including corrosion inhibitors) that includes four areas of concem. The system described by Purinton considers the several criteria and rates them from 0 to 4 ("scores" in parenthesis), where "0" is the most desirable rating. Hill also reviewed this process as applied in general to oilfield chemicals. Because of the relevance to our current review, these papers are described in detail. Some of the toxicity ratings require explanation. The effect concentration (EC) is the concentration of the chemical below, which the organisms do not display, altered behaviors. The lethal concentration (LC) is the concentration of the chemical in its environment below which it does not kill a set percentage of the organisms (usually 50%). The lethal dose (LD) is the amount of the chemical injected to kill a certain percentage of the animals. Note that chemicals with lower values are MORE toxic than chemicals with higher values. The HSE criteria are described below
Global "Restricted Use" Considerations
Note if the product and its components are listed on any of the following.
? European Union Controlled Substances (4)
? European Union Land-Banned material (4) ? North Sea Banned List (3)
? Organohalogens (non-polymeric) (4) ? CERCLA/CWA Hazardous Substance Table (3) 302.4 with RQ 100 lbm. or less
? EPA Extremely Hazardous Materials (3) ? Marine Pollutants (2)
? Resources Conservation and Recovery Act (RCRA) Waste Code U or P (4)
? California Prop 65 (2) ? Process Safety Management Chemicals List (4)
? ACDA Schedule (Arms Control Subs) (2) ? U.S. Health Department Annual Carcinogen Rep (3) ? Toxic Metals List (4)
Assessment scores for physical and chemical properties are based on the following values:
Flash point = > 141 °F (60.5°C)
73-141 °F (23-60.5 °C)
10-73°F (- 12-23 °C)
<10°F (- 12°C)
If a flammable solid, scores (0) (1) (2) (3) (Yes = 2, No = 0)
Corrisiveness" pH= <2or>12.5 (2) 2- 12.5 (0)
Reactivity: Reactivity scores are based on the material's National Fire Protection Association (NFPA) Rating (0-4) or if the material's product structure has an energy containing functional group.
If yes, score = 3, if no, score = 0.