New Experimental Rig to Investigate Abrasive–Corrosive Characteristics of Metals in Aqueous Media

Abstract

A new tribometer to investigate a conjoint effect of three-body abrasion and corrosion has been developed. In this design, a flat wear sample is loaded against a rotating cylindrical disc counterface and the abrasive slurry is delivered to the contact interface. Capabilities of the newly developed tribometer have been assessed through conducting abrasion-corrosion tests involving simultaneous electrochemical measurements. In this work, the stability of the passive layer on stainless steel under three-body abrasive wear in a near neutral electrolyte was investigated using potentiodynamic polarization tests. 316L Stainless Steel wear samples were abraded by coarse garnet particles in an aerated sodium sulphate electrolyte. The effects of load and speed on the polarization curves and passivity of 316L steel were determined. It was found that under abrasion-corrosion conditions 316L steel became more thermodynamically active and the passive corrosion rate has increased. Increasing the contact load resulted in a small increase in the passive corrosion current, while increasing the rotating speed had the opposite effect of decreasing the current. Linear polarization resistance method was used to analyse corrosion current changes with time during abrasion-corrosion testing. The existence of three distinct stages was explained by the third-body effect on the corrosion potential and current. First stage was revealed by continuous decrease of corrosion potential. Then, the potential reached a plateau for the second and third stages. In the first and second stages, particle constraint in the contact zone plays the major role and a linear rise in corrosion current with time has been recorded. After a certain amount of surface roughening, no further increase in particles entrapment is expected. Therefore, in the third stage steady-state corrosion current values are anticipated. The rig developed can also be used to simulate two-body abrasion-corrosion. The capabilities of the new rig have been compared against other experimental set-ups used in studies of combined abrasion-corrosion behaviour.

Three-Body Abrasion Corrosion Studies of High-Cr Cast Irons: Benefits and Limitations of Tribo-electrochemical Methods

“…compact passive films formed on type 304 or 316 stainless steels [43]. High current oscillations on PD curves are often recorded in corrosive wear studies of alloys that readily repassivate in the electrolyte tested [8,43]. Since significant current oscillations are absent in the abrasion corrosion PD curve in Fig.…”

“…A schematic diagram of the abrasion corrosion tribometer is shown in Fig. 1 and detailed description of the experimental set-up and its capabilities can be found elsewhere [8,14]. Corrosion-only measurements were conducted using the same set-up, with the unloaded sample and without the slurry flow.…”

“…In the last two decades, various electrochemical techniques have been adapted to tribocorrosion research and significant progress has been made in the interpretation of the tribo-electrochemical data [3][4][5][6]. While close attention has been paid to tribocorrosion testing and measurements related to a sliding contact (two-body abrasion), much less is understood about viability of tribo-electrochemical methods for testing three-body abrasion corrosion [6][7][8]. In sliding tribocorrosion a typical two-body contact involves an inert ball or pin rubbing against a metallic wear sample (working electrode) with reciprocating or unidirectional motion [3][4][5]9].…”

“…In this configuration, the ratio of wornto-unworn surface area is often low, and during the 'out-ofcontact' or 'non-friction' time the worn area of passive alloys repassivates, at least partially [10]. The most common set-up for investigating three-body abrasion corrosion is an inert ball or disc rotating against the loaded wear sample while the abrasive slurry is delivered to the contact interface [6][7][8]. The question, not answered yet, is whether the differences between two-body and three-body arrangements could affect the electrochemical measurements and data interpretation.…”

The effects of particle angularity on low-stress three-body abrasion-corrosion of 316L stainless steel

“…Tribocorrosion, defined as the conjoint action of tribological wear (mechanical damage) and corrosion (electrochemical dissolution), is a frequently encountered cause of the passive film breakdown [10,11]. Over the past two decades, various tribo-electrochemical methods have been successfully applied to elucidate how mechanical abrasion or erosion accelerate corrosion of passive stainless steels [12][13][14][15][16][17][18][19].…”