Corrosion Assessment of a Weathering Steel Bridge Structure after 30 Years of Service.

Agnieszka Królikowska,Damian Wojda,Katarzyna Zacharuk,Izabela Kunce,Urszula Paszek,Tomasz Wierzbicki,Leszek Komorowski,Katarzyna Bilewska

doi:10.3390/ma14143788

Abstract

The first steel with improved resistance towards atmospheric corrosion, the so-called weathering steel, was patented in the USA in 1933 and was initially used for coal railway cars, and after that, in building and bridge engineering. Weathering steels show higher corrosion resistance than carbon steels in many types of atmosphere due to their ability to form a compact, stable, adherent and protective patina during the time of exposure. Morphological evaluation of the appearance of the corrosion product layer, together with phase analysis of its components, can enable determination of the type of patina and the degree of protection of the steel. To support the visual assessment of a patina, a check based on the qualitative and quantitative phase analysis of its components may be carried out, and the PAI (Protective Ability Index) can be calculated. The estimation of the corrosion processes on original Polish-made weathering steel (12HNNbA) was carried out on a 30-year-old bridge in Poland. There are some structural problems within the deck derived not only from corrosion but also steel cracking, both inside and outside the boxes, at different heights. Fourteen representative samples of patina were analysed and their phase structures were determined by the X-ray powder diffraction method. The PAIs were determined and analysed.

Highlights

Published: 6 July 2021Weathering steels contain up to 2 wt.% of alloying elements such as Cr, Mn, Si, Ni, Cu, Al and Nb
Visual assessment may be unreliable, as it is the result of individual judgement and is based on the experience of the inspector
As a result of the observations and analyses performed, it was found that the steel structure did not undergo passivation in a typical manner, as described in the literature [3,4,19]

Summary

Introduction

Weathering steels contain up to 2 wt.% of alloying elements such as Cr, Mn, Si, Ni, Cu, Al and Nb. The corrosion product layer with protective properties, the so-called “patina”, is typically produced during 3 to 7 years of exposure under suitable environmental conditions, including persistent wetting and drying atmospheric cycles. The corrosion rate of weathering steel is less than 0.01 mm/year, engineering structures made from that type of structural material must be inspected periodically. Visual assessment may be unreliable, as it is the result of individual judgement and is based on the experience of the inspector. To support the visual assessment, qualitative and quantitative analysis of the components of the patina may be carried out, and the PAI may be estimated

Methods

Results

Conclusion