Corrosion-Resistant Stainless-Steel Strands for Prestressed Bridge Piles in Marine Atmospheric Environments

Abstract

This study demonstrated that stranded highly cold-worked 2205 stainless steel (SCW2205) exhibits superior corrosion resistance when compared to stranded cold-worked AISI 1080 (ASTM A416) steel and cold-worked modified austenitic stainless steel 201, making it a viable candidate for prestressing applications with extended service life. Laboratory and field testing were performed. The material microstructure was characterized using scanning electron microscopy/energy dispersive x-ray spectroscopy, transmission electron microscopy, and x-ray diffraction. Then, laboratory corrosion testing, including linear sweep voltammetry, pitting resistance exposure, and four-point bend stress corrosion cracking (SCC) testing, was performed under different conditions. These conditions included concrete pore solution saturated with chlorides, direct exposure to artificial seawater, various concentrations of NaCl and MgCl2, representative inland salt deposition conditions, and oxidizing conditions with high chloride concentrations. The laboratory studies were augmented with field testing (259 d), comprised of four-point bend SCC, U-bend SCC testing (ASTM G30), and atmospheric contaminant measurements. The pitting resistance results, corrosion morphology, stable pit safe range, SCC results in the lab and in the field, and hydrogen embrittlement (HE) testing by slow strain rate testing (SSRT) under cathodic polarization as a diagnostic showed that SCW2205 outperformed the other steels tested, in the case of marine atmospheric corrosive conditions. SCC in SCW2205 was characterized by a selective localized anodic dissolution of the ferrite matrix and environmentally assisted cracking in the austenite phase. However, SCC was only found in SCW2205 at or above 65°C. SSRTs confirmed susceptibility to hydrogen uptake and a hydrogen-assisted mechanism of HE given sufficient hydrogen. It is speculated that hydrogen uptake in pits or crevice sites might be a route to hydrogen absorption worth exploring further since the absence of cathodic polarization in application precludes hydrogen production and uptake.