Growth of anodic films on iron and stainless steel in the presence of some organic inhibitors

Abstract

Da von den Korrosionserscheinungen nur geringfugige Anteile des Rohnnaterials betroffen sind, ist auch eine deutliche Veranderung der mechanischen Eigenschaften iiber die thermische Alterung hinaus nicht wahrscheinlich. Diese Aussage wird in den langzeitigen Zeitstandversuchen im Kreislauf Crevona bestatigt, die in einem nachfolgenden Versuchsprogramrn durchgefiihrt werden.Die Nachuntersuchungen haben neben vielen detaillierten Erscheinungen vor allem gezeigt, daB die hier verwendeten stabilisierten austenitischen Stahle X 8 CrNiNb 1613 und X 10 CrNiTi 189 fur den Anlagenbau mit Natrium f i r lange Einsatzzeiten bis zu Temperaturen von 973 K anwendbar sind.Sie sind damit in gleicher Weise fiir die Anwendung mit Natrium qualifiziert wie die weltweit bevorzugten Stahle AISI 304 und 316.Wir bedanken uns auch an dieser Stelle fiir die Beitrage von Frau Z . Peric und den Herren E. Nold, D. Schlindwein und G. Wittig zu dieser Arbeit.Growth of anodic films on iron and stainless steel 161 ~~- SchrifttumEllipsometry has been used to study the influence of Benzylamine, Benzotriazole and Hexamethylenetetramine on the growth of anodic oxides on iron and on AISI 304 stainless steel in borate-buffer solutions.On iron, a limitation of the growth-rate has been observed for these substances all over the passive potential range. On AISI 304 steel, when the electrode potential exceeds 400 mV (SCE), an increase of the anodic oxide growth-rate was found in the presence of the organic substances. Adsorption on the oxide film, according to the interpretation given by Pearson, is discussed.Mit Hilfe der Ellipsometrie wurde der EinfluB von Benzylamin, Benzotriazol und Hexamethylentetrarnin auf die Bildung von anodischen Oxiden auf Eisen und dem nichtrostendcn Stahl AlSl 304 in Boratpufferlosung untersucht. Auf Eisen fiihren demnach alle drei Substanzen zu einer Begrenzung der Wachstumsgeschwindigkeit im gesamten Bereich der passiven Potentiale. Auf dem Stahl 304 hingegen bewirken die Zusatzstoffe bei Potentialen iiber 400 mV (S E) zu einer Beschleunigung der Wachstumsgeschwindigkeit der anodischen Oxide. Der Wachstumsmechanismus wird entsprechend der Deutung von Pearson unter Annahme von Adsorptionsvorgangen am Oxidfilm diskutiert.

AC Impedance Studies on Relationship between Adsorption Behavior of Polar Organic Compounds on Anodically Polarized Nickel and the HSAB Principle

“…1 and 3, the hard base compounds decreased and the soft base increased ip and Kf in the passive region for the 6B group inhibitors, whereas all of the 5B group inhibitors lowered them. It has been reported that the nitrogen containing inhibitors classified as hard bases retarded the growth rate and thickness of oxide film on iron and AISI 304 stainless steel (11). The growth rate of anodic oxide on nickel has been observed to be retarded in the presence of a benzimidazole derivative on and in the oxide film (21).…”

“…The capacity of the passive film CF is given by an equation of a parallel capacitor CF = e(,e~S/d [11] where eo and er are dielectric constants in vacuum and of the film, S surface area, and d is the thickness of the film, respectively (26). On the assumption that the impedance arises from the passive layer at 500 mV vs. SCE, C~ corresponds to C~1.…”

“…Ord and Bartlett (18) have estimated the thickness of the passive film on iron in H~SO4 by a reciprocal capacity, assuming a constant eF in Eq. [11]. If er is taken to be constant, the more resistant and thinner passive film formed on the surface inhibited with a hard base and the less resistant and thicker film with a soft base than on the uninhibited surface.…”

“…[2] has been established for a number of transition and nontransition metals and various inhibitors in HC104 solutions (6)(7)(8). The relationship between the adsorption behavior or inhibition effect of the polar compounds on oxidized metal surfaces and the HSAB principle has also been investigated (10)(11)(12)(13). [2], it has been concluded that compounds acting as soft bases were effective inhibitors against the acid corrosion of metals.…”

“…The relationship between the adsorption behavior or inhibition effect of the polar compounds on oxidized metal surfaces and the HSAB principle has also been investigated (10)(11)(12)(13). Since a highly charged metallic ion in the oxide or passive film is classified as a hard acid (1), *Electrochemical Society Active Member.…”