Nakabohtec Corrosion Protecting Co.

Ageoshimo, Japan

Nakabohtec Corrosion Protecting Co.

Ageoshimo, Japan
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Yoshida T.,West Japan Railway Company Co. | Otani S.,Nakabohtec Corrosion Protecting Co. | Takaya S.,Kyoto University | Yamamoto T.,Kyoto University | Miyagawa T.,Kyoto University
Concrete - Innovation and Design: fib Symposium Proceedings | Year: 2015

Sacrificial anode materials are installed in the border area between patch repair section and concrete section deteriorated by complex effects of carbonation and mixed chlorides induced corrosion. Protection effects are evaluated of reinforcing steel in concrete around the sacrificial anode materials where electrical resistivity of the concrete may change easily under various environmental huridity. Experiment results show that, galvanic anode system perforns to protect corrosion effectively, even if electrical resistivity of the concrete is high.


Fuda H.,Nakabohtec Corrosion Protecting Co. | Shinoda Y.,Nakabohtec Corrosion Protecting Co. | Otani S.,Nakabohtec Corrosion Protecting Co. | Matsuda Y.,East Japan Railway Company
Zairyo to Kankyo/ Corrosion Engineering | Year: 2011

It is attracted that cathodic protection method (CP) is effective in the remedy of rusted rebars, regardless of amount of salt in concrete. The aluminum galvanic anode is one of CP. Rebar potential, current density and temperature were measured at concrete rail way bridge with aluminum panel. Analysis and discussion were given to the effect by temperature shift for rebars potential, neither incident affected for depolarization by it. And, measuring time with off potential for measuring of depolarization was appropriate time.


Kobayashi H.,Port and Airport Research Institute | Yamaji T.,Port and Airport Research Institute | Akira Y.,Toyo Construction Co. | Hamada H.,Kyushu University | And 2 more authors.
Zairyo to Kankyo/ Corrosion Engineering | Year: 2013

We investigated retrofit design in cathodic protection (CP) with galvanic anodes made from an aluminum alloy. In conventional retrofit design, the decrease in CP current reduction (which affects the life of anodes) is estimated based on nominal durability values. The current reduction rate falls to a level far below the design value, leading to an increased number of facilities in which the anode life exceeds the design service life. As this trend is due to exaggerated design, it is necessary to review retrofitting methods in order to enable more effective and economical maintenance. After detailed analysis and discussion, we developed an innovative methodology for an optimized maintenance system in galvanic anode CP. To test the assumptions made, we conducted on-site, shortterm testing with an actual structure and confirmed the validity of the new design methodology. The method, which takes current reduction into consideration, allowed more accurate prediction of anode life and a reduction in the initial costs of CP facilities.


Nanasawa A.,DenkI Kagaku Kogyo Kabushiki Kaisha | Kushida J.,Nakabohtec Corrosion Protecting Co | Ueda T.,Tokushima University | Tsukagoshi M.,Tokushima University
Life-Cycle of Structural Systems: Design, Assessment, Maintenance and Management - Proceedings of the 4th International Symposium on Life-Cycle Civil Engineering, IALCCE 2014 | Year: 2015

Chloride attack and ASR are serious deterioration mechanisms of concrete structures respectively. Moreover, in the cases of marine environment and cold climate area, complex deterioration of these mechanisms can be observed because of the supply of sea water or de-icing salt. In this study, as a remedial measure against such a complex deterioration, electrochemical penetration of lithium from the electrolyte solution was investigated. It was clarified that electrolyte temperature greatly affected the extent of lithium penetration and the treatment at 40 °C remarkably accelerated lithium penetration into concrete compared with the case of 30 °C. Regarding the kind of lithium salt, LiNO3 solution was most effective among a number of different kinds of lithium salt in the viewpoints of Li+ penetration of into concrete and suppression of concrete expansion. © 2015 Taylor & Francis Group, London.


Otani S.,Nakabohtec Corrosion Protecting Co. | Yoshida T.,West Japan Railway Company | Ebina H.,Nakabohtec Corrosion Protecting Co. | Tsukamoto H.,Nakabohtec Corrosion Protecting Co. | Shinoda Y.,Nakabohtec Corrosion Protecting Co.
Zairyo to Kankyo/ Corrosion Engineering | Year: 2015

The galvanized anode system, which is often used for the cathodic protection of aluminum panels, was applied to reinforced concrete specimens of variable chloride concentration. The primary objectives of this study are the specification of the variation factor on a polarizing current and the evaluation of the steel's corrosion rate for the natural (open-circuit) corrosion and cathodic protection conditions. As a result, the polarizing current decreased as the cathodic polarization resistance and concrete resistance increased. Despite the variable chloride concentration in concrete, the corrosion rate of the natural corrosion condition was reduced compared with that of the early period. The corrosion rate of steel under cathodic protection was assumed to be equivalent to the passive current density.


Kobayashi H.,Port and Airport Research Institute | Akira Y.,Port and Airport Research Institute | Yamaji T.,Port and Airport Research Institute | Hamada H.,Kyushu University | And 2 more authors.
Zairyo to Kankyo/ Corrosion Engineering | Year: 2013

We investigated a cathodic protection design basis for reinforced concrete structures exposed to atmospheric conditions. If such structures in severely corrosive environments do not satisfy the relevant cathodic protection criteria, the situation can be remedied by supplying more current than the design value. However, as such energization results in rapid consumption of the water surrounding the anode, the voltage DC power supply may rise. Using electrochemical measurement and numerical simulation, we sought to clarify the effects resulting from environmental improvement of rebar surfaces using cathodic protection and devised a new design method. Then, via cathodic protection examination using concrete specimens affected by rebar corrosion, the validity of the new design method was determined. The approach was found to be suitable for economical and stable cathodic protection.


Mochizuki N.,Nakabohtec Corrosion Protecting Co.
Zairyo to Kankyo/ Corrosion Engineering | Year: 2010

There has been a growing demand of cathodic protection (CP) for the rehabilitation of salt damaged concrete structures. A brief introduction is given for the major CP systems used for concrete structure and the criteria of protection. In the present paper discussion is also given on the mechanism of protection, materials flow and electrical conduction within concrete, a solid system with low mobility and high electrical resistivity placed in atmosphere. Cathodic polarization protects steel reinforcement not only by shifting the metal potential in cathodic direction but also by modifying the environment factors favorable for steel protection such as an increase in pH and a decrease in chloride ion in the vicinity of metal surface resulting in protection conditions that satisfy the criteria. The environmental modification is thought to be the principal effect of CP. It is not seldom in concrete CP that a system that has been in operation below the criteria in the early stage would be changed to be satisfactory after long run owing to the modified environments. It is thus required to establish design and maintenance criteria in consideration of chronic changes.


Kodama T.,Nakabohtec Corrosion Protecting Co. | Shinoda Y.,Nakabohtec Corrosion Protecting Co. | Tanaka K.,Nakabohtec Corrosion Protecting Co.
Zairyo to Kankyo/ Corrosion Engineering | Year: 2010

In cathodic protection (CP) by impressed current method, polarization decay, a shift in potential following the switch-off of CP current, is used as parameter of adequate operation especially in the media of high resistivity, where rif-drop compensation is indispensable. Instant-off potential, sampled immediately after switch-off of CP current, is an essential parameter that represents effective ON-potential (with iR-drop compensation) and a baseline for the polarization decay. A detailed analysis of potential transient demonstrated that a transition from iR-drop to electrochemical relaxation starts within a millisecond in concrete. A novel portable instant-off potentiometer that allows direct reading of the instant-off potential was developed. The potentiometer consists of (a) generation of timing pulses for driving MOS switches and triggering an AD converter, (b) switching of CP current with variable ON/OFF interval and duty ratio, and (c) fast AD conversion triggered synchronously with ON/OFF timing followed by storing and computing the average. Noise level was minimized by properly selecting the sampling interval and by synchronizing the logging timing with the power-line wave but dispersing phase shifts of sampling points. A typical example of data logging interval and timing, duty cycle, and sampling number for averaging is shown for minimizing noise level of power-line origin. The potentiometer allowed direct display of the instant-off potential with the interval of 1.6 s. The measurements by model concrete block and concrete bridge on-site have proven the effectiveness and validity of the potentiometer.


Tanaka K.,Nakabohtec Corrosion Protecting Co. | Iwasaki T.,Kitacon Ltd.
Zairyo to Kankyo/ Corrosion Engineering | Year: 2011

On the cathodic protection system for concrete structure, a galvanic anode system is recently highlighted as maintenance-free system. But, only some reports on the periodic or continuous monitoring of its performance can be found. The report covers the continuous monitoring of the performance on our galvanic anode system with "aluminum panel anodes", applied to the concrete highway bridge. The external view on the bridge was kept in initial condition for eight months after application. Although more positive ON potential of the rebar and lower output current of anode per unit rebar surface area were observed at lower ambient temperature, the rebar potential was kept in sufficient protection level.

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