The definition of Green as it pertains to Green Chemicals or Green Corrosion Inhibition seems to be vague. Even though the scientific and engineering communities use this word frequently, there seems to be a lack of consensus on the definition. The paper describes the various definitions and their overall impact on Green.
In these days of environmental awareness and the commercial usage of the term Green, it is surprising to find no consensus definition of the term. A cursory review of technical literature as well as the Internet provides a myriad of definitions, but none with a common thread. Even the papers in the present session of the conference present various definitions.
In partnership between U.S. Environmental Protection Agency, the American Chemical Society, the Council for Petroleum Research and the National Research Council, annual Presidential Green Chemistry Challenge Awards are presented. These awards are targeted for chemical research leading to pollution reduction. The stated goal is to further ?environmentally benign chemistry?.
GREEN CORROSION INHIBITORS
A simple way of looking at Green Corrosion Inhibitors may be to focus on the production, use and disposal of these materials. This looks at the entire life cycle of the inhibitors to more efficiently produce useful inhibitors with less waste, or preferably, no waste (1). On the use side, this leads to zero emissions or zero discharge as most corrosion engineers in the water treatment industry can attest to. One of the interesting ways of achieving this is through the use of environmentally benign chemicals or inhibitors that can split after functionality into environmentally benign materials. Chemical classes and functional groups known to be toxic- as well as those that can be bioactivated into toxic substances- should be avoided in designing inhibitors.
Toxicity considerations have been used to define Green. These range from non-toxic to low toxicity materials. The target species becomes an issue. Surprisingly, one of the winners of the U.S. Presidential Green Chemistry Challenge Award was for the development of a new biocide which is toxic to target organisms and bacteria, but benign to humans and the rest of the environment. The move away from toxic phosphates, chromates and other heavy metal bearing inhibitors to non-metal bearing and low toxicity inhibitors are discussed in this symposium. One of the papers even deals with the replacement of toxic carrier solvent with a friendlier product.
Another avenue to Green Inhibitors is the use of bio-chemicals such as enzymes, which tend to behave as catalysts to control corrosion mechanisms. Lately, there has been development of enzyme catalysts that can be used in the synthesis and modification of complex polymers, including those that are chiral, electrochemically active, biodegradable or bio- compatible (1). A couple of examples of this approach are the research, by the U.S. Navy as discussed in the last NACE Research Conference, of natural enzyme adhesion promoters as corrosion inhibitors, and the research, by the University of Iowa, on the development of anti-fouling coatings for ships, which traditionally have contained heavy metals that are harmful to sea life. In this research, an enzyme embedded in the coating on a ship?s hull could potentially break down the compounds that barnacles use to attach to the hull, thus preventing fouling.
Development of corrosion inhibitors based on waste products is an approach used
