# High-Temperature Corrosion of Different Steels in Liquid Sn-Bi-Zn Heat Transfer Alloy

## TL;DR

This study examines how different steels corrode in a high-temperature heat transfer alloy, revealing significant differences in corrosion rates and material behavior.

## Contribution

The paper introduces new insights into the corrosion behavior of various steels in a Sn-Bi-Zn heat transfer alloy at high temperatures.

## Key findings

- 310S steel showed the highest corrosion layer thickness (1.50 mm) compared to 304 and 20C steels.
- XRF analysis confirmed the dissolution of Fe, Cr, and Ni into the molten alloy over time.
- Ni content was found to accelerate Sn/Zn diffusion and pore formation in the steel alloys.

## Abstract

In the fields of nuclear engineering and solar thermal utilization, low melting point alloys with excellent thermal conductivity and heat transfer performance have attracted extensive research as a new generation of heat transfer fluids, leading to many fundamental and important application issues. This study investigates the high-temperature corrosion behavior of Sn-50Bi-2Zn (wt.%) heat transfer alloy against 304 stainless steel (304), 310S heat-resistant steel (310S), and 20 carbon steel (20C) at 600 °C. Theoretical analysis, based on Fick’s diffusion law, and experimental measurements reveal significant differences in corrosion severity. After 473 h, 20 carbon steel exhibited the lowest corrosion layer thickness (0.07 mm), while 310S suffered the most severe corrosion (1.50 mm), exceeding 304SS (0.83 mm) by 81%. Diffusion coefficients derived from Sn penetration depths further quantified these trends: D310S = 2.51 × 10−7 mm2/s (6.8 × higher than 304: 3.7 × 10−8 mm2/s) and D20C = 2.87 × 10−10 mm2/s (128 × lower than 304SS). XRF analysis confirmed the dissolution of steel components into the molten alloy, with Fe, Cr, and Ni content increasing to 0.382 wt.%, 0.417 wt.%, and 0.694 wt.%, respectively, after 480 h. These results underscore the critical role of Ni content in accelerating Sn/Zn diffusion and pore formation, providing actionable insights for material selection in high-temperature heat transfer systems.