William H. Hartt

Calcareous Deposits on Metal Surfaces in Seawater—A Critical Review

Abstract While the importance of calcareous deposits to the effectiveness and efficiency of marine cathodic protection is generally recognized, there has been relatively little research directed to...

Effects of reinforcement and coarse aggregates on chloride ingress into concrete and time-to-corrosion: Part 1-Spatial chloride distribution and implications

Abstract The chloride concentration in concrete required to compromise reinforcing steel passivity and initiate active corrosion, [Cl−]th, is an important service life determinant for reinforced co...

Application of Acoustic Emission to Detection of Reinforcing Steel Corrosion in Concrete

Abstract Cracking and spalling of concrete due to corrosion of embedded steel is generally recognized as a major technological problem within the state of Florida and nationwide. Typically, this fa...

Formation of Calcareous Deposits Under Different Modes of Cathodic Polarization

Abstract Calcareous deposits that formed in natural seawater upon ASTM A710 (UNS K20747) steel polarized either potentiostatically, galvanostatically, or by a mixed-mode technique (initially galvanostatic followed by potentiostatic) have been studied. Parameters investigated included variation of current density (potentiostatic control) or potential (galvanostatic control) with time, total charge transfer, deposit thickness, thickness-to-charge ratio, deposit morphology, and deposit composition. Based upon these parameters, the mixed-mode technique was judged to provide the deposit with greatest protective properties within the time frame of the experiments. This may be related to the nature of the initial, magnesium-rich film established during he preliminary experimental period; the mechanism of calcareous deposit formation is discussed within this context.

Deep water cathodic protection: Part 2-Field deployment results

Abstract Instrumented, steel plate specimens with various levels of galvanic anode cathodic protection were deployed at a 899-m (2,950-ft) Gulf of Mexico site for 405 days. Subsequent to recovery, ...

Effect of Cement Alkalinity on Chloride Threshold and Time-to-Corrosion of Reinforcing Steel in Concrete

Abstract A series of reinforced G109-type concrete specimens with cement of equivalent alkalinity (EqA) either 1.08 or 0.32 was cyclically ponded with a 15-wt% sodium chloride (NaCl) solution and time-to-corrosion initiation, Ti, was determined. The specimens were subsequently dissected, the steel-concrete interface examined and characterized, and concrete along the top of the upper rebar sampled and analyzed for Cl−. The results revealed greater Ti and Cl− thresholds for corrosion initiation, [Cl−]th, for the higher EqA specimens; however, the data were scattered for seemingly identical specimens. In many instances, corrosion initiated preferentially at entrapped air voids at the rebar-concrete interface provided the diameter of these was ≥2.5 mm. An explanation is proposed for the site specificity of corrosion initiation and scattered [Cl−]th that considers both entrapped air voids and the spatial distribution of coarse aggregates within the Cl− ingress path.

Cracking of Concrete in Sea Water Due to Embedded Metal Corrosion

Abstract The phenomenon of concrete cracking in sea water has been investigated by impressing an anodic direct current upon the embedded metal and monitoring time to cracking. Various embedded metals were employed, and these ranked in order of increasing concrete cracking time as cadmium → zinc and copper → nickel and steel → molybdenum. Additional complementary experiments were conducted to consider the chemistry of the pore water in the vicinity of the metal-concrete interface of the impressed current specimens. These involved step-wise titration of a concrete saturated distilled water solution with various metal chlorides, and it was determined that chloride ion concentrations in the range 0.05 gms/mL can cause a pH shift to the acid range. The pH determinations from such titration experiments are in general agreement with pH measurements upon fractured faces of the concrete specimens employed in the impressed current tests. The experimental results are discussed within the frame of present theories fo...

Acoustic Emission Characterization of Corrosion Induced Damage in Reinforced Concrete

Abstract The deterioration of steel reinforced concrete caused by reinforcing bar corrosion is recognized as a major technical problem in the State of Florida and nationwide. This mode of failure i...

The Influence of Cathodic Polarization Upon Fatigue of Notched Structural Steel in Sea Water

Abstract Reverse bend fatigue tests have been conducted upon notched 1018 steel specimens in sea water as a function of constant cathodic potential. As has been reported by others, cathodic polarization was found to restore an endurance limit. The value for this parameter (endurance limit) was observed to initially increase with decreasing potential, to peak in the range −1.10 ≥ ϕ ≥ −1.25 V (SCE) and, finally, to decrease with further cathodic polarization. Interestingly, the maximum endurance limit for specimens cathodically polarized in sea water was approximately 100% greater than for fatigue in air. Possible explanations for this endurance limit enhancement are considered, and it is concluded that the calcareous deposit which commonly occurs upon cathodically polarized surfaces in sea water is either directly or indirectly responsible.

Effects of Reinforcement and Coarse Aggregates on Chloride Ingress into Concrete and Time-to-Corrosion: Part 2—Spatial Distribution of Coarse Aggregates

Abstract The chloride concentration in concrete required to compromise reinforcing steel passivity and initiate active corrosion, [Cl−]th, is an important service life determinant for reinforced co...