|Content Type||Journal Paper|
|Title||Organic Corrosion Inhibitors in Neutral Solutions; Part 1 Inhibition of Steel, Copper, and Aluminum by Straight Chain Carboxylates|
|Authors||G.T. Hefter, N.A. North, and S.H. Tan|
|Volume||Volume 53, Number 08|
|Copyright||1997. NACE International.|
|Keywords||adsorption, aluminum, aqueous solution, chain length, complexation, copper, dicarboxylates, inhibition, micelle, mild steel, monocarboxylates, polarization resistance, saline, solubility|
Much work has been done on the use of organic molecules to inhibit corrosion of metals in contact with aqueous solutions.1-8 The majority of such studies have been carried out in aggressive, usually acidic, solutions. However, it is known that the chemical form of organic inhibitors often depends upon pH (e.g., because of protonation). This, in turn, may alter their adsorbability, solubility, or complexing capability dramatically. Corrosion mechanisms also may differ significantly between acidic and neutral aqueous solutions because of the presence and/or differing nature of metal oxide/ hydroxide films at higher pH values.9-11 For these reasons, it can be misleading or even disastrous to draw conclusions about likely inhibitor effectiveness in neutral solutions on the basis of data obtained in acidic solutions.4,8,11-13 In many practical situations, such as automotive and other heat exchange systems, steam boilers, etc., solution conditions are neutral. Furthermore, the common practice of using normal tap water as the coolant or for make-up invariably introduces chloride ions (Cl), which can have a pronounced effect on corrosion behavior. There is a clear need for detailed information on the behavior of organic inhibitors in neutral solutions in the presence of Cl ions. Yet despite the vast literature on organic corrosion inhibitors, relatively few systematic studies have been made, particularly in neutral solutions.4,11 Of the various types of organic compounds available, straight chain aliphatic carboxylates show good inhibition characteristics toward a number of metals, especially mild steel.14-16 In addition, carboxylates are environmentally benign, as they have low toxicities and are readily biodegradable.
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