THE ZINC ANODE PERFORMANCE FOR SACP AN INVESTIGATION OF WARSHIP UNDERWATER STRUCTURES
4. MATERIAL/METHODOLOGY
2.1. Sacrificial Anode.
Sacrificial anode is the main component of Cathodic protection system used to protect form corrosion. Sacrificial anodes have become a standard practice for the protection of vessels and offshore hull structures against corrosion (Baere et al. 2013). Sacrificial anodes are made in various shape using alloys of zinc, magnesium and alumunium (Loto & Popoola 2011). Sacrifical zinc anodes is used to protect bare steel in commercial and military vessels, in hot waters, water storage tanks and steel reinforcing bars in concrete structurres located in marine environment (McCafferty 2010). The underwater structure of ship is protected by painting for the main protection and zinc as sacrifial anode used to control the rate of dissolution in seawater (Talbot & Talbot 1998).
In the sacrificial anode method, electrical potential is created by attaching a dissimilar metal in electrolyte, when different metals are coupled together, the anode material will release electrons and protect the cathode from corrosion (Hafizh et al. 2015). The electrode potential of low alloy steel in seawater is approximately -0,6 V vs SCE. The electrode potential of zinc is -1,0 V, thus when zinc is coupled to steel zinc will be the anode and steel will be the cathode.
The advantages are associated with sacrificial anode CP systems (Roberge 1999):
a. No external power sources required.
b. Ease of installation.
c. Unlikely cathodic interference in other structures.
d. Low-maintenance systems.
e. System is essentially self-regulating.
f. Relatively low risk of overprotection.
g. Relatively uniform potential distribution
These limitations that have been identified for ICCP systems (Roberge 1999):
a. Limited current and power output.
b. High-resistivity environments or large structures may require excessive number of electrodes..
c. Anodes may have to be replaced frequently under high current demand.
d. Anodes can increase structural weight if directly attached to a structure.
2.2. Zinc Anode.
Zinc anode are commonly available in weight from 2,27 – 113,4 kilograms (5 pounds to 250 pounds) in the form of plates, bars, and rods as shown in MIL-HDBK-1004/10. Zinc is also available as ribbon anodes in 16-millimeter by 22.2-millimeter (5/8-inch by 7/8-inch), 13-millimeter by 14.3- millimeter (1/2-inch by 9/16-inch), and 8.7-millimeter by 11.9-millimeter (11/32-inch by 15/32-inch) sizes, each with a 2.5-millimeter (1/10-inch) diameter galvanized steel wire core (Basham et al. 2003). The electrical potential of zinc anodes is approximately - 1.10 volts DC to copper/copper sulfate in soil. In some fresh waters, the potential can reverse at temperatures above 58.3 ºC (140 ºF); consequently, zinc should not be used in those cases (Basham et al. 2003).
Indonesian Naval Technology College, STTAL Postgraduate International Conference, Vol. 2 ICMST 2018 July, 26th 2018
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Fig. 4. Foundry Master Pro Fig. 3. Speciment Sample.
2.3. Method of Research.
This paper shows analysis performance of Zinc Anode on underwater structure of KRI, for evaluating performance of Zinc Anode, this paper used two method, one is chemical composition and another is based on corrosion potential measurement test. The first phase is identification of the problem, library studies, and steps of experiment.
2.3.1 Flowchart Diagram.
2.3.2 Data Collection.
a. Materials speciment.
1) Speciment A : Zinc made from Naval Laboratory.
2) Speciment B : Pure Zinc anode 99,99%.
3) Speciment C : Zinc anode from domestic market.
4) NaCl 3,5%.
b. Tools :
1) Metal Plate, Mild steel Grade A.
2) Referensial Anode.
3) Multitester.
4) Inductively Couple Plasma (IPC) for wet composition test.
5) Foundry Master Pro for dry composition test.
Table 1. Chemical Composition of Zinc Anode (Fontana 1987)
Table 2. Chemical Composition with U.S Military specification (NACE 2002)
Fig. 2. Flowchart Diagram of Research
Indonesian Naval Technology College, STTAL Postgraduate International Conference, Vol. 2 ICMST 2018 July, 26th 2018
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Fig. 6. Potential Corrosion Test.
Fig. 5. Inductively Couple Plasma
This machine contains a solid state spark source, a vacum system, an optical system and output system.
The sample was positioned on the spark stand for chemical composition analysis (Cassinath 2013).
ICP is an effective method of measuring multiple trace metals involves using an inductively coupled
plasma-atomic emission
spectrometer (Ryan & Clark 2010).
The fundamental characteristic of this process is that each element emits energy at specific wavelengths peculiar to its chemical character (Kumar, I. & Ajitha 2014). ICP instrument employs argon plasma (ICP) as the ionization source and a
mass spectrometer (MS), usually with a quadrupole mass filter, to separate the ions produced (A.A & W.L.O 2011)
Corrosion potential test is measured as a potential difference against a reference electrode at different points on a structure and is used to determine the likehood of reinforcement corrosion (Trejo, Reinschimdt & Halmen 2009). The numerical value of the measured potential difference between the steel in concrete and the reference electrode will depend in the type of reference electrode used and on the corrosion condition of the steel in concrete (Andrade et al. 2003).
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Fig. 8. Composition of Speciment B Fig. 9. Composition of Speciment C 5. RESULT AND DISCUSSION.
3.1 Result of Dry Composition Test.
The result of dry chemical composition test showed that speciment A have 99,8% (Zn), 0,121%
(Al), 0,0141% (Cd), 0,0004% (Cu), 0,0020% (Fe), 0,0087% (Pb), 0,0007% (Si).
Speciment B showed that 99,9% (Zn), 0,0045% (Al), 0,0001% (Cd), 0,0026 % (Cu), 0,0020% (Fe), 0,0111% (Pb), 0,0005% (Si).
Speciment C showed that 99,6% (Zn), 0,102% (Al), 0,0023% (Cd), 0,077 % (Cu), 0,0272%
(Fe), 0,042% (Pb), 0,0008% (Si).
3.2 Result of Wet Composition Test. The result of wet chemical composition test showed that speciment A have 1,4502% (Zn), 0,163% (Al), 0,00311% (Cd), 0,0000276 % (Cu), 0,00005% (Fe), 0,000056% (Pb).
Speciment B showed that 1,4723% (Zn), 0,0096% (Al), 0,0002% (Cd), 0,000018 % (Cu), 0,0016% (Fe), 0,00007% (Pb).
Speciment C showed that 1,456% (Zn), 0,0896% (Al), 0,00065% (Cd), 0,005 % (Cu), 0,0156% (Fe), 0,00428% (Pb).
Table 4. Result of Chemical Composition (Wet Test).
Fig. 7. Composition of Speciment A Table 3. Result of Chemical Composition (Dry
Test).
Indonesian Naval Technology College, STTAL Postgraduate International Conference, Vol. 2 ICMST 2018 July, 26th 2018
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Fig. 12. Aluminium Element
Fig. 10. Result of Corrosion Potential Test.
3.3 Result of Corrosion Potential Test.
The result of corrosion potential test without Mild Steel showed that 1,005V for speciment A, 0,977V for speciment B, 0,994V for speciment C.
Zinc with Mild steel A showed 0,83V for speciment A, 0,87V for speciment B, 0,829V for speciment C.
3.4 Comparison of Element Composition.
3.4.1 Zinc (Zn) Element
Base of theoritic graphics for Zinc (Zn) element (fig.11), showed that specimen A has 99,8%, speciment B has 99,9%, speciment C has 99,6%. Speciment B has highest value in Zinc element and speciment C has lowest.
.
3.4.2 Aluminium (Al) Element.
Base of theoritic graphics for Aluminium (Al) element (fig. 12), showed that specimen A has 0,121% in dry test and 0,163% in wet test.
Speciment B has 0,0045% in dry test and 0,0096%
in wet test. Speciment C has 0,102% in dry test and 0,0896% in wet test. Speciment B has highest value in Zinc element and speciment C has lowest. Based of grey parameters, speciment A in category for dry and wet composition test.
Table 5. Result of Corrosion Potential Test.
Indonesian Naval Technology College, STTAL Postgraduate International Conference, Vol. 2 ICMST 2018 July, 26th 2018
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Fig. 16. Ferrum Element
Fig. 14. Copper Element (dry test) Fig. 15. Copper Element (wet test) 3.4.3 Cadmium (Cd) Element.
Base of theoritic graphics for Cadmium (Cd) element (fig. 13), showed that specimen A has 0,141% in dry test and 0,00311% in wet test.
Speciment B has 0,0001% in dry test and 0,0002%
in wet test. Speciment C has 0,0023% in dry test and 0,00065% in wet test. All speciment is not in category.
3.4.4 Copper (Cu) Element.
Base of theoritic graphics for Copper (Cu) element (fig. 14,15), showed that in dry test specimen A has 0,0004%, Speciment B has 0,0026%, Speciment C has 0,0777%. In wet test, specimen A has 0,0000276%, Speciment B has
0,000018%, Speciment C has 0,005%. In dry test, Speciment A and B include in category, but Speciment C not in category. In wet test, All of Speciment include in category.
3.4.5 Ferrum (Fe) Element.
Base of theoritic graphics for Ferrum (Fe) element (fig. 16), showed that specimen A has 0,002% in dry test and 0,00005% in wet test.
Speciment B has 0,002% in dry test and 0,0016% in wet test. Speciment C has 0,0272% in dry test and 0,0156% in wet test. Speciment A and B include in category, Speciment C not in category
.
Indonesian Naval Technology College, STTAL Postgraduate International Conference, Vol. 2 ICMST 2018 July, 26th 2018
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3.4.6 Plumbum (Pb) Element.
Base of theoritic graphics for Plumbum (Pb) element (fig. 17), showed that specimen A has 0,0087% in dry test and 0,000056% in wet test.
Speciment B has 0,0111% in dry test and 0,00007%
in wet test. Speciment C has 0,0422% in dry test and 0,00428% in wet test. In dry test, all of speciment not in category, but in wet test all of speciment include in category.
6. CONCLUSION.
a. The result of dry chemical composition test showed that speciment A have 99,8% (Zn), 0,121% (Al), 0,0141% (Cd), 0,0004% (Cu), 0,002% (Fe), 0,0087%
(Pb), 0,0007% (Si). Speciment B showed that 99,9% (Zn), 0,0045% (Al), 0,0001%
(Cd), 0,0026 % (Cu), 0,002% (Fe), 0,0111% (Pb), 0,0005% (Si). Speciment C showed that 99,6% (Zn), 0,102% (Al), 0,0023% (Cd), 0,077 % (Cu), 0,0272%
(Fe), 0,042% (Pb), 0,0008% (Si).
b. The result of wet chemical composition test showed that speciment A have 1,4502% (Zn), 0,163% (Al), 0,00311%
(Cd), 0,0000276 % (Cu), 0,00005% (Fe), 0,000056% (Pb). Speciment B showed that 1,4723% (Zn), 0,0096% (Al), 0,0002% (Cd), 0,000018 % (Cu),
0,0016% (Fe), 0,00007% (Pb).
Speciment C showed that 1,456% (Zn), 0,0896% (Al), 0,00065% (Cd), 0,005 % (Cu), 0,0156% (Fe), 0,00428% (Pb).
c. The result of corrosion potential test without Mild steel showed that 1,005V for speciment A, 0,977V for speciment B, 0,994V for speciment C. Zinc with Mild steel A showed 0,83V for speciment A, 0,87V for speciment B, 0,829V for speciment C
d. Based of chemical composition test, speciment A and B is accomplished from US Military Specifications standard, but speciment C doesn’t accomplish.
e. Based of corrosion potential measurement test, all of speciment can used for sacrifice anode.