Influence of microstructure and surface treatment on the corrosion resistance of martensitic stainless steels 1.4116, 1.4034, and 1.4021

Abstract

In the last years, new approaches for the evaluation of the corrosion resistance of martensitic stainless steels were developed, which allow nearly nondestructive as well as short-term corrosion testing. This work analyzes the sensitive influence of microstructure and surface treatment on the corrosion resistance. The effect of alloy composition and microstructure, which is always present in addition to the influence of various surface treatments will be evaluated and discussed. The corrosion behavior was investigated with conventional evaluation of the pitting potential, electrochemical potentiodynamic reactivation (EPR), electrochemical noise (EN), and the "KorroPad" (KP) technique. EPR provided information about the passivation ability and the extent of chromium content reduction due to chromium carbide precipitation in the microstructure. The use of EN and KP aims to detect the influence of different surface treatment parameters on the corrosion resistance in a nearly non-destructive way. Furthermore the results shall demonstrate the functionality and convenience of the short-term corrosion test methods EN and KP in order to gain more acceptance within the scientific community. The results will allow the extraction of surface treatment effects on the corrosion behavior of the martensitic stainless steels 1.4116, 1.4034, and 1.4021.

Examination of the influence of heat treatment on the corrosion resistance of martensitic stainless steels

“…The high sulphuric concentration and the activator KSCN promote strong active dissolution of the martensitic microstructure, which inhibits passivation of the martensitic stainless steel during the measurement. The modified electrolyte used for the DL-EPR test contains 0.1 M sulphuric acid without any activator in accordance with previous work [15]. In order to guarantee an initially active surface each sample was wet ground up to grit 1000, rinsed with deionized water, cleaned with ethanol, dried and measured immediately.…”

“…The typically applied surface treatments, such as grinding, polishing and blasting will not only determine the appearance and mechanical properties of stainless steel surfaces but also have an impact on the corrosion resistance [12]. For example, homogeneous surfaces with low roughness exhibit faster and more stable passive film formation with higher corrosion protection compared to rough surfaces under the same conditions [13][14][15].…”

“…Nevertheless, there was also a successful attempt by Schultze [19] to adapt the DL-EPR test to ferritic-austenitic stainless steel grades. Previous work on martensitic stainless steels showed the possible use and application of DL-EPR to clarify unexpected pitting corrosion behavior by linking the chromium depletion detected with DL-EPR to decreased pitting corrosion resistance [15].…”

“…This method is a simple indicator test applicable without electrochemical test equipment. The KorroPad detects the susceptibility of stainless steel surfaces to pitting corrosion by a visible color reaction with a sensitivity similar to that of other electrochemical methods [12,15]. The KorroPad was originally developed for application to austenitic stainless steels but was also successfully applied to martensitic stainless steels [15].…”

“…The KorroPad detects the susceptibility of stainless steel surfaces to pitting corrosion by a visible color reaction with a sensitivity similar to that of other electrochemical methods [12,15]. The KorroPad was originally developed for application to austenitic stainless steels but was also successfully applied to martensitic stainless steels [15]. In the present work, all electrochemical test methods mentioned above were applied to two martensitic stainless steels in different heat treatment states to determine their resistance to pitting corrosion.…”