# Corrosion Behavior of Typical Engineering Structural Steels in a Plateau Valley Atmospheric Environment

## TL;DR

This study examines how different types of steel resist corrosion in a high-altitude valley environment, finding that one type performs better due to its composition.

## Contribution

The novel contribution is identifying the superior corrosion resistance of Q420qENH steel and the role of atmospheric SO2 in pit corrosion.

## Key findings

- Q420qENH steel shows better corrosion resistance due to a denser rust layer.
- Tensile stress increases both uniform and localized corrosion rates.
- Atmospheric SO2 contributes to pit corrosion by acidifying the local environment.

## Abstract

This study systematically investigated the corrosion behavior of three typical engineering structural steels (Q235, Q420, and Q420qENH) in the plateau valley atmospheric environment of the Sichuan–Tibet region using field exposure tests (including uniform corrosion and stress corrosion coupon tests), electrochemical measurements, and microscopic characterization. The results reveal that the three steels underwent predominantly uniform corrosion, accompanied by pitting corrosion, regardless of the presence of stress. Compared with Q235 and Q420 steels, Q420qENH exhibits superior corrosion resistance, which is ascribed to the denser rust layer formed as a result of its corrosion-resistant composition. Under tensile stress, both the uniform corrosion rate and pit dimensions increased significantly relative to stress-free conditions, demonstrating a pronounced accelerating effect of stress on uniform and localized corrosion. Furthermore, the enrichment of sulfur within the rust layer at the pit bottoms suggests the involvement of atmospheric SO2 in the localized corrosion process, which aggravates the breakdown of the rust layer and the acidification of the local environment at the pit bottom, thereby promoting pit growth.