Preparation and corrosion resistance properties of duplex stainless steel (00Cr22Ni6MnMoCu)

In the present paper, a new kind of duplex stainless steel (DSS, 00Cr22Ni6MnMoCu) was prepared. Cr30 was chosen as a comparison of microstructures and mechanical properties with 00Cr22Ni6MnMoCu. Corrosion tests with 3.5% NaCl solution and electrolytic solution for 00Cr22Ni6MnMoCu were carried out to analyze the corrosion pattern of test materials. It can be concluded that: (1) Austenitic and ferrite duplex stainless steel has an optimized phase distribution, high toughness and strength when the ratio of two-phase content is 1:1. (2) Corrosion tests show that the corrosion resistance of 00Cr22Ni6MnMoCu is 12 times compared to ferrite stainless steel Cr30. (3) Electrolytic corrosion tests show that for 00Cr22Ni6MnMoCu, the corrosion is caused by intergranular corrosion. For Cr30, it is mainly caused by pinholes. However, Cr30 has a poor corrosion resistance because of the presence of a large amount of carbides and their phase boundaries caused by the electric potential difference between the carbide and the matrix.

Digital Image Correlation Analysis of Corrosion Crack Behavior in a Reinforced Concrete Member

The corrosion of the internal steel bars of reinforced concrete structures is still a maintenance problem. This study aims to detect corrosion cracks in covered concrete by DIC. We proposed a new test specimen and method of electrolytic corrosion testing suitable for tracking corrosion cracks by DIC (Digital Image Correlation Analysis), and succeeded in understanding the crack initiation behavior of single and double bar specimens.

Electrolytic accelerated corrosion morphology for structural steel based on an improved solution

Atmospheric corrosion degrades the mechanical properties of steel structures mainly because of stress concentrations caused by an uneven corrosion topography. Electrolytic corrosion is regarded as one of the most efficient indoor accelerated corrosion approaches, while, the uneven atmospheric corrosion topography usually cannot be well simulated by electrolytic corrosion. This study aims to introduce an electrolytic corrosion solution suitable for simulating atmospheric corrosion. The surface morphologies of the structural steel specimens after electrolytic corrosion in three different solutions under various electrification time and magnitude of the current were compared. The surface characteristics of the corroded steel plates were measured by a 3D noncontact surface topography scanner, and analyzed based on surface roughness theory and fractal theory. The results showed that the mixed solution of 0.5% CH3COONa and 0.2% NaCl will produce pitting corrosion on the steel surface, and the surface morphologies of the steel specimens after electrolytic corrosion were consistent with that of neutral salt spray accelerated corrosion test. It is verified that the electrolytic accelerated corrosion in such a solution can simulate actual atmospheric corrosion reasonably.

Non-Destructive and Quantitative Evaluation of Rebar Corrosion by a Vibro-Doppler Radar Method

It is well known that evaluation of rebar corrosion is important for the maintenance of reinforced concrete structures, but, it is difficult to simply, quickly and quantitatively evaluate the amount of corrosion of rebars embedded in concrete by conventional non-destructive evaluation (NDE) methods such as electrical, electromagnetic and mechanical method. This paper proposes a vibro-Doppler radar (VDR) measurement method to quantitatively evaluate rebar corrosion by measuring the vibration ability of the rebar forcibly vibrated in concrete by an excitation coil. It is experimentally demonstrated in RC test pieces that the rebar vibration displacement obtained by developed VDR method is valid and is less affected by the moisture in the concrete. In addition, simultaneous monitoring of the rebar vibration displacement of the test pieces is performed through an electrolytic corrosion test and the measured vibration displacement is compared to the rebar corrosion loss evaluated. As the results, it is cleared that the rebar vibration displacement starts to increase from slightly before the occurrences of corrosion crack on the concrete surface as the corrosion loss increases. It is also shown that the rebar vibration displacement becomes 4 times higher than that in initial condition at the rebar corrosion loss of 250 mg/cm2. This implies that the VDR has potential to nondestructively and quantitatively evaluate rebar corrosion in concrete.

Corrosion Characteristics of Anchor Cables in Electrolytic Corrosion Test and the Applicability of the Test Method in Study of Anchor Cable Corrosion

The selection of corrosion test method in the corrosion study of the prestressed anchors is an important issue. In this paper, the corrosion test of anchors was conducted with electrolytic corrosion test method. The corrosion characteristics of the anchor cables were examined. The effects of sodium chloride solution concentration, current, test time, and prestress level on corrosion were studied. The applicability of electrolytic corrosion method in anchor cable corrosion study is discussed subsequently. The results show that the corrosion of the anchor appears to be uniform corrosion. With the corrosion of the anchor, the central wire of the cable was basically not corroded, and the cross-sectional shape of the outer wire changes from a round to fan shape. The sodium chloride concentration and prestress level have no obvious effects on the corrosion of the anchor. The variation of test time does not affect the difference between the measured and theoretical calculated results, while a proper current in the electrolysis test may help reduce the difference. The measured corrosion rate fluctuates from −4% to 10% and tends to be higher compared with calculated results based on Faraday’s law. The study indicates that the electrolytic corrosion test is applicable in the anchor corrosion study.

Predicting the Width of Corrosion-Induced Cracks in Reinforced Concrete Using a Damage Model Based on Fracture Mechanics

Using a finite-element scheme based on a damage model, a numerical system is developed to predict cracks in reinforced concrete beams due to corrosion expansion. The numerical results show that the width of such cracks is affected considerably by (i) the shape of the reinforcing bar, (ii) the presence of stirrups, and (iii) the number of main reinforcement bars. Specimens of reinforced concrete beams are fabricated to simulate those used in the analysis, and we determine how the crack width is related to the amount of the reinforcing bar corrosion through electrolytic corrosion experiments. The experimental results are used to assess the validity of the numerical ones, and the latter are considered to reproduce the former.