Effect of Conductive Coating on Silver/Silver Chloride Electrodes for Cathodic Protection Application

Measurement of pipe to soil potential in a cathodic protection system is something that must be done which aims to monitor the performance of


A B S T R A C T
Measurement of pipe to soil potential in a cathodic protection system is something that must be done which aims to monitor the performance of the installed cathodic protection system.The main measuring tool in measuring pipe to soil potential is the reference electrode.The stability of the reference electrode is important as a validation of the measurement results.So far, the stability of the reference electrode is very difficult to maintain due to frequent changes caused by the environment, especially for permanent reference electrodes that are buried in the underground or installed in seawater.Permanent reference electrode sensors commonly used in seawater is the Ag/AgCl reference electrode, but in fact the Ag/AgCl reference electrode is generally unstable and must be stabilized with a KCl solution and other problems have not been produced in Indonesia.This research will be carried out by adding a conductive layer to the Ag/AgCl electrode so that its stability can be increased.The sensor manufacturing process starts from pretreatment, electrolysis and product characterization.The results of the best coating thickness and weight gain experiments showed by the highest voltage variations and time variations (4000mV and 60 minutes).The presence of conductive solid material increases corrosion resistance from 0.00391 mm/year to 0.19549 mm/year and increases the stability of the Ag/AgCl layer ± 5 mV.

Natural Sciences Engineering & Technology Journal (NASET Journal)
One type of permanent reference electrode sensor commonly used in seawater is the Ag/AgCl reference electrode.Its main function is to measure the potential value (protection) of the cathodic protection given to structures in seawater.The Ag/AgCl reference electrode used to measure the degree of structural protection is generally unstable and must be stabilized with a KCl solution.The process of Ag/AgCl instability is caused by the environment of the electrode, which can cause corrosion on the AgCl layer besides that, the instability of the AgCl layer on the Ag/AgCl electrode. 8- 11 he study aimed to make a permanent Ag/AgCl reference electrode and utilize solid polymer media as an Ag/AgCl environment so that the stability of the reference electrode can be maintained.

Tools and materials
The equipment used in this research were Metller AE200 digital scales, SANFIX SP-305E power supply, optical microscope, heater, 100 ml measuring cup, 250 ml beaker glass, petri dish, mounting block, multimeter SANWA PC700, thermometer, grinding machine and potentiostat.The materials used in this research were KCl powder, water, silver wire, platinum wire, conductive polymer, resin and catalyst, cooper wire, seawater, and sandpaper grade 1000 to 5000.

Research procedure
This research procedure begins with making an AgCl layer on the silver wire, and then the results will be compared if using a conductive layer with one that does not use a conductive layer.Diagrammatically, the research procedure can be seen in Figure 1.Silver wire was cut with a length 5 cm and then pretreated with distilled water, soapy water, and lime juice.These silver wire ends are connected with copper wire that has been formed in such a way.250 ml of 1M KCl solution was prepared.The power supply is connected to the ends of the poles with cables whose ends have been given alligator clamps.Silver and platinum wires were connected to each pole of the power supply and then dipped into 1M KCl solution with time variations of 15, 30, 45, and 60 minutes and voltage variations of 1000, 2000, 3000, and 4000 mV.
The wire is removed and dried, the AgCl will stick to the silver wire, and then the silver wire will be blackgray Figure 2. AgCl mechanism process. 12

Microstructural analysis
Microstructural analysis was carried out by metallographic method according to ASTM E3-11 standard.In this test, etching was carried out with a solution according to the ASTM 20 standard, then the results of the microstructural picture were taken, then compared with the literature and analyzed.

Coating thickness analysis
Coating thickness analysis was carried out by visual inspection using an optical microscope.

Weight Analysis
Analysis of weight was carried out by weighing the difference in the initial weight of Ag before and after going through the electroplating process using an AE200 digital scale.

SEM & EDX analysis
SEM & EDX analysis was performed using a JEOL SEM instrument (JED-2200 Series).The test sample is placed on the aluminum holder using glue adhesive.
The sample is put into a vacuum chamber, while electrons are generated from the filament and then accelerated so that they hit the sample.The results of the SEM and EDX images can then be analyzed.

Polarization analysis
Polarization test analysis was carried out by Gamry reference 600 potentiostat instrument equipped with an application Gamry framework.The potentiodynamic test was carried out at -0.25 V to 0.25 V for corrosion potential (vs.Eoc).The scan rate used is 0.167 mV/s according to the ASTM G5 standard.
The polarization test was carried out on two samples, namely the Ag/AgCl sample coated and uncoated by a conductive solid material with the same variation of time and voltage.

Corrosion potential analysis
Potential testing was carried out using the PC700

Microstructural analysis
Based on Figure 3, it can be analyzed that the grain shape of the specimen and the literature have similarities where the grain shape is not straight and has a puzzle-like shape (jigsaw) but does not have a 100% similarity due to the different magnification of the images taken, from these observations it can be concluded that the samples taken use is pure silver.From these data, it can be analyzed that the greater the voltage applied to the specimen, the thickness of the AgCl layer on pure Ag will increase.This is caused by increasing the amount of voltage flowing during the electroplating process.The number of Cl-ions will be more released from K+ so that the amount of Clreleased from the solution will precipitate or stick to the workpiece. 10,12From these data, it can be analyzed that the longer the electroplating process of Ag to Ag/AgCl, the thickness of the AgCl layer on pure Ag will increase.This is because the longer the electroplating process lasts, the portion of the accumulated movement of electrons and material transfer at the two electrodes also increases.

AgCl film weight with various voltage and time analysis
From Figure 8, it can be analyzed that the greater the voltage, the weight gained on the specimen will increase.This is due to the increasing amount of voltage flowing during the electroplating process.The more Cl-ions will be released from K+ so that a large amount of Cl-released from the solution will precipitate or stick to the workpiece.From these data, it can be analyzed that the longer the processing time, the weight gained on the specimen will increase.This is due to the longer the process takes place electroplating, the portion of the accumulation of electron movement and material transfer at the two electrodes will also increase.Cl-which binds to Ag+ and will increase weight gain.

Potential analysis
Potential measurements were carried out using a data logger, which was recorded for up to 500 hours to see the stability of the Ag/AgCl electrode potential (Figure 11).This potential data recording was carried out for up to 500 hours, and it was seen that the Ag/AgCl electrode coated with a solid conductive material looked more stable than the ordinary Ag/AgCl electrode (Table 1).
Figure 11.Data logger open circuit potential record Ag/AgCl with and without conductive layer.

Figure 9
Figure 9 (b) is a photo of the results of the SEM test taken using a magnification of 1000 X in an area of the sample.It is clearer that there is porous AgCl in the Ag metal where the white part is Ag while the black part is Porous AgCl, but not all parts of Ag turn into

Table 1 .
Open circuit potential record of Ag/AgCl.