Influence of the surface state on the Initiation of Crevice Corrosion on stainless steels

Abstract

Results from sea-water and laboratory exposure tests with multiple crevice assemblies are presented. The results from tests on austenitic and ferritic-austenitic stainless steel samples subjected to various surface treatments demonstrate that an acid treatment greatly improves the crevice corrosion resistance of previously ground surfaces. Pickling in dilute sulphuric acid and passivation in nitric acid has thereby virtually the same beneficial effect as the common nitric + hydrofluoric pickling acid. The beneficial effect of pickling and passivation is related to the removal from the surface of sulphide inclusions, being potential nucleation sites for the initiation of discrete pitting attacks preceding the onset of crevice corrosion. Potentiodynamically determined pitting potentials and results from testing in I O Y FeCI, . h H 2 0 according to ASTM G 48-76 show poor correlation with results from sea-water exposures.Vorgelegt werden Ergebnisse von Lagerversuchen in naturlichem Mccrwnsser und im Lahoratorium; dabei wurden Probenanordnungen rnit Mehrl'achspalten benutzt. Die Ergebnissc mit austenitischen und fcrritisch-austenitischen Stahlen verschiedener Oberflachenzustande zeigen. daR eine Behandlung mit SBure die Spaltkorrosionsbestandigkeit von geschliffenen Oberflachen betrachtlich verbessert. Beizen in verdiinnter Schwefelsaure und Passivieren in Salpetersaure haben dabei praktisch den gleichen giinstigen Effekt wie das iibliche Beizen i n Salpetersgure + FluBsHure. Die giinstige Wirkung des passivierenden Beizens beruht auf der Entfernung der an der Oberflaehe befindlichen Sulfideinschliisse. die Keimstellen liir Lochkorrosion bilden, die der Spaltkorrosion vorangeht. Die potentiodynamisch ermittelten I.ocIikorrosioiis~~~~t~~iti;llc sowic die Ergehnisse von Vcrsuchen in 10% FeC1, . 6 H1O (ASTM G 48-76) zeigen schlechte Ubereinstimni ti rig mi t dcn in Mecr\vaaac I c rhal t c ncii Ergc bn i ~s e n .

In Vitro Corrosion Behavior of Lingual Orthodontic Archwires

“…Electrochemical measurements of OCP and E b showed a considerable variability among samples of the same alloy. Surface variations can influence the results obtained due to differences in surface finishing and surface defects [30][31][32][33][34][35].…”

Correlation between Corrosion Potential and Pitting Potential for AISI 304L Austenitic Stainless Steel in 3.5% NaCl Aqueous Solution

“…The Ep value is the potential at which a sudden increase in the current is observed. However, for a given metal (considered as having a given chemical composition and a given microstructure) the Ep value obtained by this technique depends on the following testing variables: the potential scanning rate [2][3][4][5][6] , the surface finish of the sample [7][8][9][10][11][12] , the aeration conditions of the electrolyte 13 , the immersion time prior to the test 6,8 , and the geometry of the sample 14 . Moreover, the obtained anodic curve does not always yield a precise measurement of Ep.…”

Corrosion performance of 316L SS and titanium modified austenitic stainless steels in the bleaching stages

“…The compositions of the alloys are almost similar except for the free titanium content. Literature reports[18, 19] revealed that, the presence of titanium in the solid solution sufficiently improves the pitting corrosion resistance. It has also been reported[20] that the presence of titanium in the passive film may reduce its ionic and electronic conductivities.…”