Study on Degradation Law and the Equivalent Thickness Model of Steel Subjected to Sulfate Corrosion

Abstract

In order to study the variation of mechanical properties of steel under acid rain corrosion conditions in northern China, monotonic tensile tests were conducted on Q235 steel with a thickness of 3.0 mm and 4.5 mm using a method of artificially prepared simulated acid rain solution for indoor accelerated corrosion. The results show that the failure mode of corroded steel standard tensile coupon includes normal fault and oblique fault. The failure patterns of the test specimen show that the thickness of the steel and corrosion rate affected the corrosion resistance. Larger thicknesses and lower corrosion rates will delay the failure mode of corrosion on steel. The strength reduction factor (Ru), deformability reduction factor (Rd) and energy absorption reduction factor (Re) decrease linearly with the increasing corrosion rate from 0% to 30%. The results are interpreted also from the microstructural point of view. The number, size, and distribution of the pits are random when the steel is subjected to sulfate corrosion. The higher the corrosion rate, the clearer, denser, and more hemispherical the corrosion pits. The microstructure of steel tensile fracture can be divided into intergranular fracture and cleavage fracture. As the corrosion rate increases, the dimples at the tensile fracture gradually disappear and the cleavage surface gradually increases. An equivalent thickness reduction model is proposed based on Faraday’s law and the meso-damage theory.

Axial Compressive Behaviours of Coal Gangue Concrete-Filled Circular Steel Tubular Stub Columns after Chloride Salt Corrosion

“…We propose a simplified method for predicting the ultimate bearing capacity of C-CFST columns undergoing corrosion that is based on Chinese Standard GB50936-2014 [ 50 ], Technical Code for Concrete-Filled Steel Tubular Structures and Zhang et al [ 44 ], as given by the following: where N 0 is the unmodified design strength of the C-CFST columns (N), A sc is the total cross-section (mm 2 ), and f sc is the compressive strength for the C-CFST columns (MPa). f sc is given by where and ξ the hoop coefficient of C-CFST is with f ye as the yield strength of the steel tube after corrosion, f c the compressive strength of a concrete cylinder, and θ se the steel ratio after corrosion exposure.…”

“…The equations for calculating the mechanical properties of the steel tube as a function of the corrosion rate, according to Ref. [ 44 ], are shown in Equations (2) and (3). f ye represents the tensile yield strength of the steel with various ρ (unit: MPa).…”