ii Acknowledgments iii List of Figures vii List of Tables x Notations xi 1.0 Introduction 1 1.1 Background 1 1.2 Deterioration Models 1 1.3 Scope of Study 3 2.0 Review of Corrosion of Steel in Concrete 2.1 Background 5 2.1.1 Mechanism of Electrochemical Corrosion 5 2.1.2 Pourbaix Diagrams 7 2.1.3 Polarization 8 2.1.4 Passivity 11 2.1.5 Growth of Rust Film 11 2.2 Corrosion of Steel in Concrete 12 2.2.1 Concrete as an Electrolyte 12 2.2.2 Principles of Steel Corrosion in Concrete 16 2.2.3 Initiation of Steel Corrosion in Concrete 19 2.2.4 Corrosive Activity of Concrete 21 2.3 Corrosion Monitoring Techniques 25 2.3.1 Half-cell Potential 25 2.3.2 Linear Polarization Technique 26 2.3.3 AC Impedance 28 2.3.4 Gravimetric Technique (Weight Loss Method) 28 2.3.5 Techniques for Determining the Chloride Content 29 2.4 Summary 29 3.0 Review of Time to Cracking Models 32 3.1 Cady-Weyers' Deterioration Model 32 3.2 Bazant’s Mathematical Models of Time to Cracking 32 3.3 Morinaga’s Empirical Equation of Time to Cracking 34 3.4 Other Metal Loss Criteria to Cracking 35 3.5 Some Comments on Existing Model s 36

Modeling the Time-to Corrosion Cracking of the Cover Concrete in Chloride Contaminated Reinforced Concrete Structures

This paper develops an integrated computational methodology for chloride-induced degradation assessment of reinforced concrete structures by considering all three phases of the deterioration process. The chloride penetration process is simulated using a finite element-based method by following an analogous transient thermal analysis. A reinforcement corrosion and rust expansion model based on Faraday’s law is developed, and the rust expansion is characterized by an equivalent time-varying radial displacement boundary condition. Two established corrosion rate models – the constant model and the dynamic model – are included in the rust expansion model. Finite element analysis with a smeared cracking approach is implemented to simulate the rust expansion and the associated concrete cracking process. Simulation results are presented for a reinforced concrete slab exposed to a constant chloride environment.

Chloride-induced reinforcement corrosion and concrete cracking simulation

Corrosion of stainless steel coated with TiN, (TiAl)N and CrN in aqueous environments

A poly-acetamide-acetoxyl methyl-propylsiloxane (PAAMPS) polymer containing a cerium (Ce) oxide-derivative was synthesized through three spontaneous reactions: condensation, amidation, and acetoxylation. The PAAMPS synthesizing took place between the Ce acetate dopant and aminopropylsilane triol (APST) as the film-forming precursor aqueous solution at 150°C. PAAMPS was evaluated for use as a corrosion-preventing coating for air-cooled condensers consisting of two metal components: aluminum fins and carbon steel tube. The key factors to ensuring the maximum performance of the PAAMPS/Ce oxide coating system in mitigating the corrosion of both aluminum and steel included (1) minimizing the content of non-reacted water-soluble APST and Ce acetate remaining in the coating, (2) lowering the susceptibility of the coating’s surface to moisture, (3) precipitating a passive Ce3+ oxide (Ce2O3) film insensitive to Cl dissolution over the metal’s surfaces, and (4) possessing excellent adhesion to the metal’s surfaces. The combination of these factors considerably decreased the rate of the cathodic oxygen reduction reaction at the corrosion site of the metals. In fact, the corrosion rate, measured in milli-inches per year (mpy), of bare steel was reduced more than one order of magnitude by applying this coating. Correspondingly, the coating extended the useful lifetime of steel exposed in a salt-fog chamber at 35°C from only ∼10 hr to ∼768 hr. Furthermore, this coating system far better protected an aluminum substrate from the corrosion than it did one of steel. Even a very thin nanoscale coating film deposited on the aluminum’s surfaces reduced the corrosion rate, (mpy), by nearly two orders of magnitude over that of the bare aluminum. Also, the salt-spray resistance of aluminum panels covered by this nanoscale film was strikingly extended to more than 1440 hr, compared with ∼40 hr for bare aluminum.

Cerium acetate-modified aminopropylsilane triol: A precursor of corrosion-preventing coating for aluminum-finned condensers

An amino‐based protic ionic liquid as a corrosion inhibitor of mild steel in aqueous chloride solutions

Breakdown of the thin air-formed oxide film is the first step in the corrosion of steel exposed to aqueous chloride environments. We studied oxide-film breakdown by observing changes, with time, of appearance, weight loss, and corrosion potential while varying the three components of the system: environment, substrate, and film. Environment was varied by changes in chloride and hydrogen peroxide concentrations. Low carbon steel, stainless steel, aluminum, and titanium substrates were studied. Various types of crystalline oxide film were applied to steel substrates by RF sputtering. The results of this work demonstrated that the chemical and electronic properties of the oxide film on steel are inconsequential in determining whether film-breakdown will occur. We interpret these results in terms of a film-breakdown mechanism in which substrate dissolution begins at film defects and spreads, thus causing removal of the film by undercutting. According to this model, the ability of the substrate to spo...

L. Allegra

Papers

Breakdown of Oxide Films on Steel Exposed to Chloride Solutions