Elsevier

Corrosion Science

Volume 165, 1 April 2020, 108411
Corrosion Science

Synergistic effect of corrosion and wear of the 316 stainless steel in molten zinc alloy at 460 °C

https://doi.org/10.1016/j.corsci.2019.108411Get rights and content

Highlights

  • Tribo-corrosion of stainless steel in molten zinc alloy is studied.

  • Without wear, Fe2Al5Znx layer forms and protects steel from dramatic corrosion.

  • The synergy of corrosion and wear accounts for 90 % of material loss.

  • Corrosion induces brittle scale and embrittlement at subsurface, accelerating wear.

  • Wear promotes formation of less-protective FeZn10 scale, accelerating corrosion.

Abstract

The failure of 316 stainless steel under tribo-corrosion in molten zinc alloy (Zn-0.2Al, wt%) at 460 °C was investigated and compared with corrosion or the sole wear. In the absence of wear, intact Fe2Al5Znx layer forms and protects the steel from dramatic corrosion. Without liquid-metal corrosion, the steel suffers from plastic deformation on friction and slight adhesive wear. While for tribo-corrosion, the synergy of corrosion and wear accounts for 90 % of material loss. Firstly, corrosion generates a brittle scale and leads to embrittlement at subsurface, which accelerate wear. Secondly, wear promotes the formation of less-protective FeZn10 scale, accelerating corrosion.

Introduction

Liquid metal is now arousing worldwide attention owing to its unique properties, such as adjustable viscosity, high thermal conductivity, self-healing [[1], [2], [3], [4], [5]]. From the tiny self-powered soft robot to the huge coolant in nuclear reactor, liquid metal finds application in various new fields (energy, machinery, electronics, etc.) [[6], [7], [8], [9], [10]]. It promotes the development of modern industry, meanwhile it brings in some problems to the metallic components contacted with it, e.g. corrosion [11,12]. Take the advanced nuclear reactor as an example, liquid lead and lead-bismuth eutectic are the two primary candidate coolant. But at high temperatures they cause severe corrosion, which accompanied with the poor compatibility, giving a challenge for the selection of the containment materials. [13].

Instead of the individual corrosion, it has been reported that, for moving parts, abrasion wear would act together with the liquid metal corrosion, accelerating the material failure [[14], [15], [16]]. In fuel cladding tubes and heat exchanger (HX) tubes, fretting, a particular type of wear, of the outer wall takes place as a result of flow induced vibrations. Coupled with the liquid metal corrosion, fretting destroys the tubes at an increased speed [15,16]. Del Giacco [14] reported that the fretting groove formed on the T91 steel could reach 40.5 μm in depth after only 120 h corrosion in molten lead alloy. Comparing to that, more rapid failure by the synergy of liquid metal corrosion and wear was found in the continuous hot dip galvanizing line [[17], [18], [19], [20]]. The sink roll soaped in zinc-pot should be repaired every 14–30 days [18]. This high maintenance ratio is related to the serious corrosion and wear it suffered [19].

Until now, although the problem of corrosion wear in liquid metal is widespread, there is still lack of a model to explain it. With reference to the tribo-corrosion in other corrosive media, a basic model is as follows [21]:VCW=VW+VC+ΔVSwhere VCW is the total material volume loss, VW is the volume loss due to individual wear, VC is the volume loss due to individual corrosion, ΔVS is the volume loss by synergistic effect of wear and corrosion. It is noteworthy that, ΔVS usually accounts for a large proportion of the VCW [21]. For example, the corrosion rate of 316 stainless steel in static molten zinc at 460 °C was merely 0.2 g/h, while just under a friction load of 10 N, the substrate loss has increased to 51.4 g/h [5]. Obviously, the synergy of corrosion and wear accounts for the fast deterioration of the stainless steel in liquid metal. By now, available researches are mainly focused on the simple evaluation of corrosion resistance of certain alloys or coatings in liquid metal, rather than on how the tribo-corrosion takes place and goes on [[22], [23], [24], [25], [26], [27], [28], [29], [30]]. In fact, revealing the underlying tribo-corrosion mechanism is of fundamental scientific interest as well as technological importance in the further study of optimizing alloy composition and adjusting working conditions in factory.

In this paper, tribo-corrosion of the 316 stainless steel in molten zinc alloy was investigated. The chosen steel and the liquid metal (Zn-0.2Al, wt%) are referred to the real working environment in continuous hot dip galvanizing line. The underlying tribo-corrosion mechanism is elucidated and compared with that of the individual corrosion by the zinc alloy or wear in air at 460 °C.

Section snippets

Equipment design and operation

A high temperature tribo-corrosion equipment is assembled. Its structure is schematically shown in Fig. 1. This test rig is designed to stimulate the operating process of sink roll in the molten zinc alloy. It includes the following five units: driving, supporting, loading, heating and lifting. For the driving unit, a motor (marked with M in Fig. 1a) drove the holder to rotate at a constant rate through a belt. A cylindrical sample (marked with S in Fig. 1b) was screwed on the bottom of the

Kinetics

Fig. 2 shows corrosion rate in liquid alloy (individual corrosion) and wear rate of the 316 stainless steel on rubbing in air (individual wear) or in molten zinc alloy (tribo-corrosion) at 460 °C. In Fig. 2a, the mass loss of the steel in molten zinc increases gradually during the whole 90,000 rotation cycles of corrosion. The weight loss grows fast at first and even takes two thirds of the total loss after 36,000 cycles. Thereafter, corrosion rate becomes moderate with the extension of soaping

Discussion

In this paper, tribo-corrosion behavior of the 316 stainless steel in molten Zn-0.2Al alloy was studied and compared with its individual corrosion or wear at 460 °C. When the steel is suffered from tribo-corrosion in molten zinc alloy, its volume loss reaches to 143.1 × 10−4 mm3/(Nm), while it is merely 4.9 × 10−4 mm3/Nm for individual wear in atmosphere after 90,000 rotation cycles. Meanwhile, the mass loss of the steel after individual corrosion is only 17.4 mg/cm2 in this liquid alloy. We

Conclusion

In this study, tribo-corrosion behavior of 316 stainless steel in molten zinc alloy was studied and compared with its individual corrosion or wear at 460 °C. The following conclusions can be drawn:

  • (1)

    After individual corrosion in the molten zinc alloy, intermetallic compound of Fe2Al5Znx forms at the steel surface. Although this phase is partly dissolved and converted into FeZn13Alx phase by reaction with the outside molten zinc alloy, the continuous Fe2Al5Znx layer retards largely zinc invasion

Data availability

The raw/processed data required to reproduce these findings cannot be shared at this time due to technical or time limitations.

CRediT authorship contribution statement

Zhongdi Yu: Methodology, Data curation, Writing - original draft, Visualization. Minghui Chen: Conceptualization, Formal analysis, Writing - review & editing, Funding acquisition, Supervision. Fengjie Li: Methodology, Resources. Shenglong Zhu: Supervision. Fuhui Wang: Supervision, Project administration.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This project is financially supported by the National Key R&D Program of China under Grant No. 2017YFB0306100, the National Natural Science Foundation of China under Grant No. 51871051, and by the Fundamental Research Funds for the Central Universities under Grant No. N180212008.

References (40)

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