Zinc as a Self-Regulating Galvanic Anode For Ship Hulls

CORROSION ◽  
1960 ◽  
Vol 16 (10) ◽  
pp. 491t-496t ◽  
Author(s):  
J. A. H. CARSON
Keyword(s):  
Cathodic Protection ◽  
High Purity ◽  
Sea Water ◽  
Self Regulation ◽  
Type Systems ◽  
Current Output ◽  
Zinc Anode ◽  
Ship Hulls ◽  
Protection Systems ◽  
Satisfactory Method

Abstract This report presents results of service trials of up to three years duration for high purity and alloyed zinc hull anodes. The trials demonstrated that zinc anodes of suitable composition are capable of providing complete cathodic protection for ship hulls for extended periods in sea water. The current output of alloyed anodes (0.3% aluminum or 0.1% aluminum + 0.05% cadmium) is reliable and predictable because these materials do not polarize with time. Zinc hull anodes of suitable design can have useful current outputs for periods of eight to ten years in sea water. Bolting is a satisfactory method of fastening zinc anodes to a ship's hull. Zinc anodes cause little or no accelerated break-down of the adjacent hull paint. The two outstanding advantages of the zinc anode systems namely, self-regulation and improved current distribution, are available at a competitive price. Compared to the cheapest of the controlled type systems, whether of the galvanic or impressed voltage type, the zinc anode system at 13 cents per sq. ft. per year costs: (a) slightly more for large wetted hull areas of around 50,000 sq. ft., (b) slightly less for hull areas of around 15,000 sq. ft. and (c) markedly less for smaller hull areas. Recommendations are made for: (1) The more widespread use of zinc anodes for cathodic protection systems both on and in ships. (2) The use of high purity (ASTM Special High Grade) zinc alloyed with either aluminum, or aluminum plus cadmium, as the standard zinc anode material for all sea water applications. 5.2.2

The Low Potential Zinc Anode In Theory and Application

CORROSION ◽  
1961 ◽  
Vol 17 (11) ◽  
pp. 550t-556t ◽  
Author(s):  
J. R. WELLINGTON
Keyword(s):  
Cathodic Protection ◽  
Sea Water ◽  
Self Regulation ◽  
Anode Current ◽  
Cathode Polarization ◽  
Current Output ◽  
Zinc Anode ◽  
A Value ◽  
Protection Systems ◽  
Circuit Resistance

Abstract After a brief discussion of the principles of cathodic protection and the basic requirements of a galvanic anode, anode requirements are examined specifically in terms of the cathodic protection of iron or steel in an electrolyte of uniform characteristics. For sea water it is shown that it is desirable to limit the cathode polarization to a value less anodic than −1.1 v (vs Ag/AgCl). The advantages of a low potential anode for the cathodic protection of iron under these conditions are discussed in detail in terms of circuit resistance, self-regulation, and cunrent distribution on the cathode. Other desirable anode characteristics such as current efficiency, current capacity per unit volume, and the effect of anode shape on anode current output are examined mathematically. The practical advantages and implications of the above considerations are described. It is suggested that where cathode polarization controls current distribution on the cathode and regulates anode current output, a new concept can be advanced for the design of cathodic protection systems utilizing low potential zinc anodes. 5.2.2

The Current-Voltage Relationship Of Galvanic Anode Arrays in Cathodic Protection★

CORROSION ◽  
1958 ◽  
Vol 14 (6) ◽  
pp. 47-52
Author(s):  
L. J. WALDRON ◽  
M. H. PETERSON
Keyword(s):  
Cathodic Protection ◽  
Sheet Steel ◽  
Initial Current ◽  
Current Output ◽  
Specific Data ◽  
Ship Hulls ◽  
Current Voltage ◽  
Sea Wall ◽  
Relationship Of ◽  
Current Voltage Relationship

Abstract The current output of full-scale arrays of several anode sizes in use by the U. S. Navy for the cathodic protection of ship hulls were determined. Impressed-current anodes formed from sheet steel were substituted for conventional galvanic anodes to reduce the weight and number of arrays necessary to obtain the desired information. Five anode sizes were investigated. A 1500-foot steel sea wall located in water with a resistivity of 34 to 38 ohm-cm acted as an un-polarizable cathode. The output currents were determined for driving potentials of 0.1, 0.2, 0.5, 0.7, and 1.0 between the cathode and the anode arrays; hence the data can be used to estimate for any galvanic material both the initial current output of an anode array, and the continuing current output against a cathode polarized to a known potential. The anodes in all arrays investigated suffered mutual interference as indicated by decreased current outputs from individual anodes as the number of anodes in the array increased. It was found that the addition of anodes is more efficient than a moderate separation of anodes in increasing the total current output. An empirical equation was derived from the data of the continuous linear arrays which relates the current output to total anode area and driving potential. It may be used to estimate the current output of arrays for which more specific data have not been obtained, but these estimations should be confirmed by experimentation wherever possible. 5.2.2

Corrosion Test about Interference of Cathodic Protection Systems in Marine Concrete Structure

2014 ◽  
Vol 894 ◽  
pp. 129-133 ◽  
Author(s):  
Jin A Jeong
Keyword(s):  
Cathodic Protection ◽  
Concrete Structure ◽  
Corrosion Test ◽  
Limited Information ◽  
Stray Current ◽  
Zinc Anode ◽  
Protection Systems ◽  
Marine Concrete ◽  
Ti Mesh ◽  
Interference Problems

When unprotected structures are nearby to CP systems, interference problems between unprotected and protected structures may be occurred. The stray current interference can accelerate the corrosion of nearby structures. During a recent few decades the protection technologies against stray current induced corrosion have been significantly improved and a number of techniques have been developed. However, there is very limited information in marine environments. In this study, cathodic protection systems installed both the ICCP with Ti-mesh anode and the SACP with zinc anode has been adopted to verify the current influence through laboratory experiment. CP potential and current have been investigated, moreover, 4 hour depolarization test has been involved to reveal the effectiveness of cathodic protection.

Rehabilitation measures for Champlain Bridge, Montreal, Canada

1996 ◽  
Vol 23 (6) ◽  
pp. 1326-1340 ◽  
Author(s):  
G. P. Carlin ◽  
M. S. Mirza ◽  
M. Gaudreault
Keyword(s):  
Cathodic Protection ◽  
Prestressed Concrete ◽  
Concrete Beams ◽  
Pilot Project ◽  
Concrete Surface ◽  
Zinc Anode ◽  
Bridge Rehabilitation ◽  
Prestressed Girders ◽  
Protection Systems ◽  
Control Corrosion

Major rehabilitation of the Champlain Bridge, Montreal, Quebec, has been undertaken with the goal of restoring its overall integrity. The bridge is a major transportation link carrying over 42 million vehicle transits annually. Repairs to all elements of the structure have recently been under way, such as deck replacement, pier repairs including submerged regions, restoration to prestressed girders, implementation of cathodic protection to control corrosion, new drainage provisions, and crash barriers. Rehabilitation of the main steel truss spans over the St. Lawrence Seaway is presented elsewhere. Testing of two cathodic protection systems on prestressed concrete beams has been undertaken with the goal of full-scale installation on all 50 affected spans. A possible pilot project is being examined, which incorporates the use of zinc anode spray applied to the concrete surface to act as passive, or induced current type, or as a combination of active and passive systems on the different sections of the bridge. Key words: bridge rehabilitation, cathodic protection systems, condition survey, corrosion protection strategy, external prestressing, honeycombing and spalling, impervious membrane, injection of cracks, prestressed concrete beams, underwater pier repairs.

A Study on Galvanic Current Variation of Zn Sacrificial Anode Made by Including of Additive in Solutions with Various Conductivities

2018 ◽  
Vol 926 ◽  
pp. 25-30
Author(s):  
Kyung Man Moon ◽  
Myeong Hoon Lee ◽  
Tae Sil Baek
Keyword(s):  
Structural Steel ◽  
Fresh Water ◽  
Current Density ◽  
Cathodic Protection ◽  
Sea Water ◽  
Sacrificial Anode ◽  
Galvanic Current ◽  
Zinc Anode ◽  
Protection Method ◽  
Steel Piles

There have been two cathodic protection methods to inhibit corrosion of the structural steel piles which are being immerged under seawater, or to control corrosion of a hull part of the ship exposed to sea water. One of them is a sacrificial anode cathodic protection method that the steel pile can be protected with galvanic current by potential difference between sacrificial anode and corrosive structural steel. And, the sacrificial anode cathodic protection method have generally merits compared to impressed current method because it can be easily applied to everywhere which is not connected with electricity. However, when the steel piles are being submerged in low conductivity solution mixed with fresh water and sea water, the structural steel piles mentioned above have not been protected occasionally perfectively due to decreasing of galvanic current of zinc anode caused by deposited with oxide film on the surface of anode. In this study, four types of zinc anodes samples which are included with three types of additives such as NaCl, KCl, and ZnCl2were prepared, and galvanic currents, the polarization characteristics of these anodes was investigated using electrochemical methods such as polarization curves, impedance, cyclic voltammogtam and galvanic current in order to evaluate the effect of additive affecting to quality of zinc anode. The sample added with NaCl indicated the highest value of galvanic current density compared to other samples in the case of lower and higher conductivity solutions such as 0.32 and 2.97mS respectively, and the sample added with KCl revealed the smallest galvanic current density in middle value of conductivities such as 1.53 and 2.27 mS. Moreover, Zn sample no added with additive exhibited the smallest value of galvanic current density in the lowest conductivities such as 0.32 and 0.98 mS. Therefore, it is considered that the galvanic current of the sacrificial anode can be increased by adding of additive when the anode is submerged in low conductivity solution mixed with fresh water and sea water.

scholarly journals Cathodic protection of structures in seawater using solar panels

2019 ◽  
Vol 121 ◽  
pp. 02004
Author(s):  
Boris Borisovich Chernov ◽  
Van Mung Vu ◽  
Anac Maskharovich Nugmanov ◽  
Lyudmila Yuryevna Firsova
Keyword(s):  
Cathodic Protection ◽  
Sea Water ◽  
Cathode Current Density ◽  
Complete Agreement ◽  
Low Alloy Steels ◽  
Solar Panels ◽  
Protective Properties ◽  
Theoretical Concepts ◽  
Alloy Steels ◽  
Cathode Current

It is well known that the cathodic protection of structures in seawater is accompanied by the formation of calcareous deposits on them. In current study, we consider the physicochemical modelling of the formation of the deposit composition against cathode current density in seawater. The reliability of the model representations is confirmed by direct experiments. The work also studied the protective properties of the deposits with a different composition for low-alloy steels in natural sea water. It has been shown that the deposits of pure Mg(OH)2 and the deposits of CaCO3 + Mg(OH)2 had better protective ability against corrosion than the deposits of pure CaCO3. However, the deposits of Mg(OH)2 dissolved faster than the deposits of CaCO3 and CaCO3 + Mg(OH)2. Theoretical concepts and experiments on the laws governing the formation of the deposits and their protective properties are in complete agreement with each other. This allows to use the obtained patterns in the cathodic protection of structures in sea water using solar panels, forming standard deviations with predetermined protective properties in the daytime.

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