Corrosion inhibition solutions

Corrosion Inhibition. Another important property of antifreeze solutions is the corrosion protection they provide. Most cooling systems contain varied materials of constmction including multiple metals, elastomeric materials, and rigid polymeric materials. The antifreeze chosen must contain corrosion inhibitors that are compatible with all the materials in a system. Additionally, the fluid and its corrosion inhibitor package must be suitable for the operating temperatures and conditions of the system. 

The corrosion of tin by nitric acid and its inhibition by n-alkylamines has been reportedThe action of perchloric acid on tin has been studied " and sulphuric acid corrosion inhibition by aniline, pyridine and their derivatives as well as sulphones, sulphoxides and sulphides described. Attack of tin by oxalic, citric and tartaric acids was found to be under the anodic control of the Sn salts in solution in oxygen free conditions . In a study of tin contaminated by up to 1200 ppm Sb, it was demonstrated that the modified surface chemistry catalysed the hydrogen evolution reaction in deaerated citric acid solution. 

Atmospheric corrosion can be prevented by using volatile inhibitors which need not be applied directly to the surfaces to be protected. Most such inhibitors are amine nitrites, benzoates, chromates, etc. They are mainly used with ferrous metals. There is still some disagreement as to the mechanism of action. Clearly, any moisture that condenses must be converted to an inhibitive solution. There is no doubt that the widely used volatile inhibitors are effective in aqueous solutions containing moderate... 

The mechanisms of corrosion inhibition will be described separately for acid and neutral solutions, since there are considerable differences in mechanisms between these two media. Definitions and classifications of inhibitors are given in Section 17.2 and by Fischer. ... 

Recent developments in the mechanisms of corrosion inhibition have been discussed in reviews dealing with acid solutions " and neutral solu-tions - . Novel and improved experimental techniques, e.g. surface enhanced Raman spectroscopy , infrared spectroscopy. Auger electron spectroscopyX-ray photoelectron spectroscopyand a.c. impedance analysis have been used to study the adsorption, interaction and reaction of inhibitors at metal surfaces. 

The inorganic nitrite used as a corrosion inhibitor in aqueous alkylene glycol or polyoxyalkylene glycol solutions can be replaced with polyoxyalkylene amines [1263,1264]. Such polyoxyalkylene amines impart corrosion inhibition to the liquid in contact with the metal and the metal in contact with the vapors of the aqueous composition. Aqueous compositions containing the glycol and the polyoxyalkylene amine also exhibit a low foaming tendency. 

Corrosion inhibition of mild steel in acid solutions by 2-aryl-5-oxadiazolinethiones (2-hydroxyphenyl, 2-phenyl, and 2-cinnamyl) has been observed <2002MCH425>. The potentiodynamic polarization data have shown that compounds studied predominantly behave as cathodic inhibitors in acid solutions. 

Electrochemical impedance spectroscopy was used to determine the effect of isomers of 2,5-bis( -pyridyl)-l,3,4-thiadiazole 36 (n 2 or 3) on the corrosion of mild steel in perchloric acid solution <2002MI197>. The inhibition efficiency was structure dependent and the 3-pyridyl gave better inhibition than the 2-pyridyl. X-ray photoelectron spectroscopy helped establish the 3-pyridyl thiadiazoles mode of action toward corrosion. Adsorption of the 3-pyridyl on the mild steel surface in 1M HCIO4 follows the Langmuir adsorption isotherm model and the surface analysis showed corrosion inhibition by the 3-pyridyl derivative is due to the formation of chemisorbed film on the steel surface. 

A great research interest concerns zinc corrosion inhibition. Chromate solutions were used [289-293] for the inhibition of zinc corrosion. The surface film contained a mixture of zinc oxide and hydroxide of chromium(III). Different behaviors of the passivated zinc electrode was observed depending on the cation of the used chromate [293]. 

This method is, of course, a sophisticated empiricism, but it allows the corrosion efficiency of any organic to be rapidly estimated. The reservation is that there must have been some prior data on corrosion inhibition for the system concerned (e.g., Fe in acid solution) to provide the learning graph. 

In thinking about corrosion inhibition, it is implicitly assumed that one is dealing with a metal. This is fair enough in considering corrosion in acid solution, but the... 

Corrosion inhibitors are organic or inorganic species added to the solution in low concentration and that reduce the rate of corrosion. Inhibition can function in three different ways ... 

The various simple chromate anions including chromate, Cr042-, dichromate, Cr2072, and bichromate, HCr04, have all been reported to be potent corrosion inhibitors when they are present as soluble species in solution. Chromate is an effective inhibitor for Al, Fe, Mg, Cd, Sn, and many other metals and alloys. The specific form of the anion present in solution depends on its concentration and solution pH (21). Because evidence of corrosion inhibition has been detected over very wide ranges of soluble Cr(VI) ion concentration and pH, each of these species appears to possess inhibiting properties. 

Corrosion inhibition is often brought about by adsorption of some material in the solution, and this may be one of the reaction products. Van Name and Hill (3) found that Ag did not dissolve in ferric alum solutions as fast as other metals, and that the rate was decreased by the silver ion formed or by added silver sulfate. 

Copper does form compounds with BTA in solutions. The pH of the solution influences the stability of these compounds and thereby the effectiveness of their corrosion inhibition. For the same reason, for this chemical, pH also influences the removal of BTA from a copper film after copper CMP. The reaction between BTA and copper favors the release of BTA at low pH. In order to minimize organic contamination, the interaction between the organic chemical and the film to be polished has to be... 

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