scholarly journals Corrosion and Cathodic Protection at Disbonded Coatings

1996 ◽  
Author(s):  
J. H. Payer ◽  
K. M. Fink ◽  
J. J. Perdomo ◽  
R. E. Rodriguez ◽  
I. Song ◽  
...  
Keyword(s):  
Corrosion Rate ◽  
Metal Surface ◽  
Current Distribution ◽  
Cathodic Protection ◽  
Computational Models ◽  
Corrosive Environment ◽  
Laboratory Measurements ◽  
Applied Potential ◽  
Local Areas ◽  
Control Corrosion

The effectiveness of cathodic protection to control corrosion and the resulting corrosion rate of pipelines arc determined by the chemical and electrochemical conditions at local areas along the pipeline. The disbonding of coatings and tapes is also controlled to a large extent by the chemical and electrochemical conditions. Processes that occur on the metal surface and their effect on corrosion and cathodic protection are discussed with respect to real pipeline conditions. Disbonded coatings on steel can interfere with the current distribution from cathodic protection. Shielding the current under disbonded coatings can affect the level of protection, the corrosion behavior and the disbonding of coatings. A major thrust in our laboratories has been the use of laboratory measurements and computational models to determine the changes in the corrosive environment that occur beneath disbonded coatings as a function of applied potential, disbonded area geometry, prior corrosion products and wet/dry cycles. These results are summarized here.

Determination of corrosion rate in places of insulation damage of underground pipelines

2020 ◽  
Vol 2020 (48) ◽  
pp. 35-42
Author(s):  
R.M. Dzhala ◽  
◽  
B.Ya. Verbenets’ ◽  
V.R. Dzhala ◽  
V.P. Lozovan ◽  
...  
Keyword(s):  
Corrosion Rate ◽  
Corrosion Protection ◽  
Current Distribution ◽  
Cathodic Protection ◽  
Polarization Resistance ◽  
Cathodic Polarization ◽  
Electromagnetic Method ◽  
Insulating Layer ◽  
Underground Pipelines

The electromagnetic method of non-contact current measurements makes it possible to quickly monitor the state of passive (insulating coatings) and active (cathodic polarization) corrosion protection of underground pipelines (UP); detect places of unsatisfactory insulation, determine the transient resistance and its components (resistances of soil, insulating layer, polarization) in different sections, the area of insulation damage, the current distribution of cathodic protection of UP. In combination with contact measurements of direct and alternating voltages, ohmic and polarization potentials, it is possible to determine the polarization resistance and estimate the corrosion rate.

Anwendung des kathodischen Korrosionsschutzes für den Bewehrungsstahl in Beton / Applications of Cathodic Protection to Steel in Concrete

2000 ◽  
Vol 6 (6) ◽  
pp. 655-668
Author(s):  
L. Bertolini ◽  
F. Bolzoni ◽  
L. Lazzari ◽  
P. Pedeferri
Keyword(s):  
Corrosion Resistance ◽  
Reinforced Concrete ◽  
Hydrogen Embrittlement ◽  
Corrosion Rate ◽  
Cathodic Protection ◽  
Operating Conditions ◽  
Throwing Power ◽  
Control Corrosion ◽  
Chloride Contaminated ◽  
Prestressed Structures

Abstract The paper deals with the application of cathodic protection of steel in atmospherically exposed reinforced concrete. The use of this technique to control corrosion rate in chloride contaminated constructions and to improve the corrosion resistance of reinforcement in new structures expected to become contaminated is discussed. The more recent applications of cathodic protection on carbonated concrete are also considered. For each type of application, principles and operating conditions (potential and current applied, throwing power, risk of hydrogen embrittlement in the case of prestressed structures) are discussed. Examples of cathodic protection and prevention in bridges, and buildings are reported.

scholarly journals Study of Overprotective-Polarization of Steel Subjected to Cathodic Protection in Unsaturated Soil

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4123
Author(s):  
Mandlenkosi G. R. Mahlobo ◽  
Peter A. Olubambi ◽  
Phumlani Mjwana ◽  
Marc Jeannin ◽  
Philippe Refait
Keyword(s):  
Raman Spectroscopy ◽  
Corrosion Rate ◽  
Cathodic Protection ◽  
Steel Surface ◽  
Open Circuit Potential ◽  
Protective Layer ◽  
Progressive Increase ◽  
Open Circuit ◽  
Applied Potential ◽  
Protective Ability

Various electrochemical methods were used to understand the behavior of steel buried in unsaturated artificial soil in the presence of cathodic protection (CP) applied at polarization levels corresponding to correct CP or overprotection. Carbon steel coupons were buried for 90 days, and the steel/electrolyte interface was studied at various exposure times. The coupons remained at open circuit potential (OCP) for the first seven days before CP was applied at potentials of −1.0 and −1.2 V vs. Cu/CuSO4 for the remaining 83 days. Voltammetry revealed that the corrosion rate decreased from ~330 µm yr−1 at OCP to ~7 µm yr−1 for an applied potential of −1.0 V vs. Cu/CuSO4. CP effectiveness increased with time due to the formation of a protective layer on the steel surface. Raman spectroscopy revealed that this layer mainly consisted of magnetite. EIS confirmed the progressive increase of the protective ability of the magnetite-rich layer. At −1.2 V vs. Cu/CuSO4, the residual corrosion rate of steel fluctuated between 8 and 15 µm yr−1. EIS indicated that the protective ability of the magnetite-rich layer deteriorated after day 63. As water reduction proved significant at this potential, it is proposed that the released H2 bubbles damage the protective layer.

Adsorption and corrosion inhibition characteristics of two medicinal molecules

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Hydrochloric Acid ◽  
Corrosion Rate ◽  
Mild Steel ◽  
Corrosion Inhibition ◽  
Half Life ◽  
Thermodynamic Data ◽  
Inhibition Efficiency ◽  
Gravimetric Method ◽  
Corrosive Environment ◽  
Corrosion Inhibition Efficiency

The corrosion inhibition characteristics of two medicinal molecules phenylalanine and rutin on mild steel in 1.0M Hydrochloric acid were evaluated using gravimetric method. Corrosion inhibition efficiency of 83.78 and 90.40 % was obtained respectively after seven days. However, phenylalanine showed weak accumulative higher corrosion inhibition efficiency. The presence of both molecules in the corrosive environment reduced the corrosion rate constant and increased the material half-life. Thermodynamic data calculated suggests a spontaneous adsorption of the molecules on the mild steel’s surface.

Potential in microroughness domain of metal surface employed in cathodic protection mode

2021 ◽  
Vol 2021 (3) ◽  
pp. 48-54
Author(s):  
V. Lukovich ◽  
◽  
V. Kartuzov ◽  
Keyword(s):  
Mathematical Model ◽  
Metal Surface ◽  
Cathodic Protection ◽  
Computational Experiment ◽  
Computational Domain ◽  
Protective Potential ◽  
Long Time ◽  
Protection Mode ◽  
Model Equations ◽  
Iterative Procedures

This effort presents the results of investigation of cathodic protection process of a section of the main pipeline, which has been operating in cathodic protection mode for a long time and which insulation has completely exfoliated from metal surface, and a cavity between is filled with water and salt impurities. In this case, a decisive factor is a fact that a metal surface is covered with microroughnesses in the form of protrusions with almost conical shape. The surface is immersed in electrolyte. At the electrolyte-metal interface, a potential difference is formed - a corrosion potential, which creates an unstable equilibrium among the potentials of metal and electrolyte. A mathematical model is designed and implemented into a numerical algorithm and computer program. A computational experiment has been carried out to calculate the potential around microroughness. The model describes a change in potential in this area at incomplete and complete cathodic protection of metal surface. The basis of computational model is a selection of one of metal protrusions of material microheterogeneity and placing it in a cylinder, which diameter coincides with that one of the lower base of this protrusion, and its upper part passes through the apex of the protrusion. Mathematical model equations with corresponding boundary conditions and their discrete implementation are presented. The solution of problems is obtained by iterative procedures based on reference values of protective potential taken from practice. The results of computational experiment are presented in the form of graphs: 1) potential distribution in the field of electrolytes; 2) changes in electrolyte potential at the border with protrusion at different values of polarization potential; 3) changes in polarization resistance in the area (calculated). The geometry of computational domain was also varied, and the values of protective potential were determined to ensure the absence of corrosion. Keywords: corrosion, microroughness, protective potential, plastic current density, electrolyte

scholarly journals Corrosive Environment Assessment and Corrosion-Induced Rockbolt Failure Analysis in a Costal Underground Mine

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Qifeng Guo ◽  
Jiliang Pan ◽  
Min Wang ◽  
Meifeng Cai ◽  
Xun Xi
Keyword(s):  
Chemical Composition ◽  
Corrosion Rate ◽  
Time Dependent ◽  
Gold Mine ◽  
System Failure ◽  
Corrosive Environment ◽  
Support Design ◽  
Ph Values ◽  
Environment Assessment

As an effective ground-reinforcing system, rockbolts have been widely used in underground excavations. Corrosion of rockbolts has been one of the most reasons for rockbolts system failure. In this paper, the chemical composition and pH values of the groundwater in Sanshandao Gold mine are first tested. Corrosion of the slotted rockbolts used in roadways of the mine is analysed. The corrosion rate of rockbolts is evaluated based on experimental results from similar corrosive conditions. A time-dependent analytical model on anchoring force degradation caused by corrosion of the rockbolt is developed. Furthermore, the effects of corrosion rate and geometric parameters of the slotted rockbolts on anchoring force degradation are discussed. Suggestions on rockbolts support design in corrosive conditions are given. It has been found that, with the corrosion time increasing, the anchoring force between the rock and the rockbolt gradually decreases. The larger the corrosion rate is, the faster the anchoring force decreases. For long-term service roadways under corrosive conditions, a slotted rockbolt with a smaller radius and thicker wall can enhance the anchoring force.

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