Investigations proofing the passive layer stability of stainless steels

The corrosion resistance of stainless steels is massively influenced by the condition of their surface. The surface quality includes the topography of the surface, the structure and composition of the passive layer, and the surface near structure of the base material. These factors are influenced by final physical/chemical surface treatments. The presented work shows significantly lower corrosion resistance for mechanical machined specimens than for etched specimens. It also turns out that the rougher the surface, the lower the corrosion resistance gets. However, there is no general finding which shows if blasted or grinded surfaces are more appropriate, but a dependency on process parameters and the characteristics on corrosive exposure in terms of corrosion behavior. The results show that not only the surface roughness Ra has an influence on corrosion behavior but also the shape of peaks and valleys which are evolved by surface treatments. Imperfections in the base material, like sulfidic inclusions lead to a weaker passive layer, respectively, to a decrease of the corrosion resistance. By using special passivating techniques the corrosion resistance of stainless steels can be increased to a higher level in comparison to common passivation.

Section: System Components Experimental Work and Discussion Of Inflmentioning

confidence: 98%

Section: System Components Experimental Work and Discussion Of Inflmentioning

confidence: 99%

Section: System Components Experimental Work and Discussion Of Inflmentioning

confidence: 99%

See 1 more Smart Citation

Influence of the surface condition on corrosion behavior of stainless steel

Gümpel

Hörtnagl

2016

“…The high costs of stainless steels are primarily due to the alloying elements nickel and molybdenum. Thus research and industry are seeking for possible alternatives as documented also in several papers by Jürgen Mietz et al . In order to replace the standard austenitic stainless steels 1.4301 (18/8 CrNi steel) and 1.4401 (18/8/2 CrNiMo steel) lean duplex steels, ferritic stainless steels and manganese alloyed austenitic steel were investigated by exposure tests in natural and artificial environments and by electrochemical investigations.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical and XPS surface analytical study on the reactivity of Ni‐free stainless steel in artificial saliva

Elsener

Pisu

Fantauzzi

et al. 2016

Nowadays there is a strong demand to replace CrNi stainless steels used for biomedical applications such as brackets in orthodontics with a new generation of more biocompatible austenitic, nickel-free alloys. The aim of this work is the investigation of the growth and stability of the surface films formed on DIN 1.4456 Ni-free stainless steel (18% Cr, 18% Mn, 2% Mo) in artificial saliva (pH 7.9) at 37°C by electrochemistry and XPS surface analyses and the assessment of the ions that leach from the steel. These results show that the open circuit potential asymptotically increases and the corrosion current density decreases from 1 to 24 hours exposure time to the artificial saliva. XPS provides evidence that the surface film present on the surface after mechanical polishing transforms into a passive film that becomes progressively enriched in Cr(III) oxy-hydroxides whereas iron and manga¬nese oxides are depleted. It is found that the instantaneous corrosion rate decreases exponentially with the amount of Cr(III) in the passive film. The results are discussed regarding the biocompatibility, thus the release of ions into solution, of the new nickel-free stainless steel. Based on the results presented in this paper and literature evidence a comprehensive model is proposed that substantiates the biocompatibility of these alloy

“…The indicator turns blue by contact with iron ions. Therefore corrosion at imperfections of the passive layer can be located . All samples were tested with three KorroPads which remained on the surface for 15 min.…”

Section: Methodsmentioning

confidence: 99%

Influence of grinding parameters on the corrosion behavior of austenitic stainless steel

Reinemann

Rosemann

Babutzka

et al. 2019

Samples of the austenitic stainless steel grade X5CrNi18-10 (1.4301, AISI 304) were ground industrially with various grinding parameters to study their influence on corrosion resistance. The ability of the mechanically ground surfaces to form a stable passive layer was evaluated by KorroPad test and a modified electrochemical potentiodynamic reactivation test based on a single loop (EPR-SL). Furthermore, the surfaces were characterized by surface analytical methods. The main influence was determined regarding abrasive belt type. Surfaces mechanically ground with granulate abrasive belts constantly had a lower corrosion resistance than surfaces ground with single-coated grain.The granulate abrasive belts generated more sensitized surface areas and left formations of welded sample material on the mechanically ground surfaces. A post-treatment with a nonwoven abrasive proved to be an effective finishing process by which the surface defects and sensitized material got removed and the surfaces regained the expected corrosion resistance. K E Y W O R D Sabrasive belt, austenitic stainless steel, electrochemical potentiodynamic reactivation, grinding process, KorroPad, surface