Overview and Application Examples of GC-Compass
GC-Compass is the only device and OS independent software tool on the market for the prediction of galvanic corrosion and assessment of materials galvanic compatibility. Designers, engineers, architects, consultants, maintenance and inspection personnel can quickly assess and quantify the impact of galvanic coupling of dissimilar metals on the remaining life of their components or systems anytime, anywhere, on any device running any OS without the need to install or download anything. Unlike other galvanic corrosion prediction software based on the static "curve crossing" methodology valid only for the conditions under which the polarization curves were measured for a very limited number of alloys in artificial seawater at 25oC, GC-Compass utilizes machine learning and cloud computing to accurately model the effects of temperature, cathode to anode area ratio, the environment variables (sea water, 3.5%NaCl solutions, fresh water, tap water, distilled water, marine atmosphere, industrial atmosphere) on the rate of galvanic corrosion for over 250 metal-to-metal and metal-to-CFRP composite galvanic couples. In addition to the prediction of galvanic corrosion rate, GC-Compass also predicts the material compatibility class and the remaining life of the component or structure based on the exposure conditions in the field.
Users of GC-Compass start by selecting the dissimilar metal couple from the dropdown list. The database has over 250 galvanic couples and is updated regularly with more couples added to the list. Figures below show the screen shots of GC-Compass.
Figure 1 GC-Compass Predicts Galvanic Corrosion Rate and Galvanic Compatibility Class for over 250 Metals, Alloys and CFRP Composite Materials.
The current database includes the following metals, alloys, and CFRP composite galvanic couples:
Ag - Au
If you cannot find the couple of your interest in the list, do let us know through the Contact Us link and we will conduct the necessary tests to generate the required data for inclusion in the software, free of charge for licensed users of GC-Compass.
Figure 2 GC-Compass Predicts Galvanic Corrosion and Galvanic Compatibility Class for over 250 Metals, Alloys, and CFRP Composite Galvanic Couples.
After selecting the galvanic couple, the next step is to select the environment relevant to your application. The dropdown list in Figure 3 below has 7 options from seawater to industrial atmosphere, representing the natural environments. If your process fluids are not listed in the dropdown menu, you should choose one of the waters that closely matches the chloride level in your process fluids. WebCorr can customize GC-Compass for your specific process fluids and alloys used in any industry from general engineering to wafer fabrication.
Figure 3 GC-Compass Models the Effects of Seven Types of Environments on Galvanic Corrosion and Galvanic Compatibility Class.
The next step is to enter the temperature of the environment. Temperature is a critical factor that influences the rate of corrosion. Some galvanic couples such as zinc-steel and aluminium-steel will reverse the polarity at certain temperatures, meaning the usual anodes (zinc and aluminium) have become the cathodes with respect to steel when the temperature exceeds certain threshold value, as shown in Figure 4 below.
Figure 4 GC-Compass Predicts the Polarity Reversal for Zinc in Zn-Carbon Steel Couple.
GC-Compass models the effects of temperature and the cathode to anode area ratio on the corrosion rate of the anodic member of the couple and the galvanic compatibility. Other galvanic corrosion prediction software based on the static "curve crossing" methodology simply fails to model the critical effects of temperature and the cathode-to-anode area ratio on the galvanic corrosion rate and galvanic compatibility. The outputs from the GC-Compass software include:
Figure 5 GC-Compass Models the Effects of Temperature and Cathode to Anode Area Ratio on Galvanic Corrosion and Galvanic Compatibility Class.
GC-Compass is not only powerful for the prediction of galvanic corrosion and assessment of galvanic compatibility of metals and alloys, it is also equally powerful for the prediction of the corrosion rate of a single metal when it is not galvanically coupled to another metal. This can be done easily by setting the "cathode to anode area ratio" to zero, then the anode metal in the selected couple is effectively corroding independently without the influence of galvanic effect. Now you can change the temperature or the environment and see the predicted remaining life of the anode metal without the influence of galvanic corrosion. This is another unique feature in GC-Compass that is not found in other galvanic corrosion prediction software based on the static "curve crossing" methodology. WebCorr's corrosion prediction software and corrosion modeling software utilize machine learning and cloud computing to optimize the predictive engines such that all contributing factors to the corrosion process are accurately processed. The prediction and modeling results are validated against field data, not the artificial seawater at 25oC used by other software based on the static "curve crossing" methodology.
Service Life Prediction for Fasteners
GC-Compass can be a particularly powerful tool for predicting the performance or service life of fasteners. For example, the SS316 fasteners used on AA6061 plates exposed to seawater at 60oC can be accurately predicted using the "effective thickness of anode". Assuming that the fastening assembly will fail when the hole in the AA6061 plates loses 0.35 mm thickness (or the diameter of the hole increases by 0.70 mm), GC-Compass predicts that the SS316-AA6061 assembly exposed to seawater at 60oC would fail in just over 5 months (Figure 6a) below.
Figure 6a GC-Compass Predicts the Galvanic Compatibility and the Service Life of Fasteners
Numerous fastener configurations (metallic materials both ferrous and non-ferrous, with metallic coatings such as cadmium, nickel, zinc and galvanizing, and CFRP composites) exposed to seawater, fresh water, tapwater, distilled water, marine atmosphere and industrial atmosphere can be assessed and evaluated at the design stage before service failures occur in the fields. For example, Figure 6b shows that aluminum alloy AA7075 is compatible with titanium alloy Ti-6Al-4V exposed to marine environment at 25oC. No significant galvanic effect is expected under the specified conditions. However, when the temperature is increased by 10oC to 35oC which is entirely expected in military aircrafts operating in many parts of the world, the compatibility class shifted to Class II: borderline condition with significant galvanic corrosion rate at 0.177 mm/y, as shown in Figure 6c. Other galvanic corrosion prediction software based on the static "curve crossing" methodology simply fails to model this critical effect of temperature on the galvanic compatibility.
Figure 6b GC Compass Predicts the Compatibility of AA7075 with Ti-6Al-4V Fasteners
Figure 6c GC-Compass Models the Critical Effect of Temperature on the Galvanic Compatibility of Fasteners
Service Life Prediction for Process Piping in Semiconductor Manufacturing
In semiconductor manufacturing, the process cooling water is frequently contaminated with copper ions, which will deposit on AA6061 piping surface and induce pitting corrosion in AA6061. The temperature of process cooling water is about 90oC and the pipe wall thickness is 2.85 mm. Tap water in GC-Compass closely matches the chloride level in the process cooling water. With these basic information (Figure 7), GC-Compass predicts that the piping would leak in approximately 2.5 years after operation due to the galvanic effect of AA6061 and the copper deposit. Other galvanic corrosion prediction software based on the static "curve crossing" methodology simply fails to model this critical effects of temperature and service environment on the galvanic compatibility and the remaining life.
Figure 7 GC-Compass Predicts Service Life of Process Piping in Semiconductor Manufacturing.
Service Life Prediction for Structures in Marine and Seawater Services
AA6061 plate and carbon steel structural members were used for the construction of a vessel for seawater services. The effective cathode to anode area ratio is 11.04. The vessel leaked just over 2 years after commencing operation. The galvanic compatibility between AA6061 and carbon steel predicted by GC-Compass is Class III, which means the two materials are not compatible in the seawater environment, and the time-to-leak predicted by GC-Compass is 2.031 years (Figure 8). Other galvanic corrosion prediction software based on the static "curve crossing" methodology simply fails to model this critical effect of cathode to anode area ratio on the galvanic corrosion rate and galvanic compatibility in seawater.
Figure 8 GC-Compass Predicts the Service Life of Structures in Marine and Seawater Services
Service Life Prediction for Carbon Steel Storage Tank with Stainless Steel 304 Clad Bottom
In a major expansion program, a plant installed several hundred large storage tanks. Most of the older tanks were made of ordinary carbon steel and completely coated on the inside with a baked phenolic paint. The solutions in the tanks were only mildly corrosive to steel but contamination of the product was a major consideration. The coating on the floor was damaged because of mechanical abuse and some maintenance was required. The tops and sides were made of steel, with the sides welded to the stainless steel (304) clad bottoms. The steel was coated with the same phenolic paint, with the coating covering only a small portion of the stainless steel below the weld. A few months after start-up of the new plant, the tanks started failing because of perforation of the side walls. It was observed that most of the holes were located within a 2-inch band above the weld. This is a classic galvanic corrosion case involving the question of which metal to coat -carbon steel or stainless steel. In GC-Compass (Figure 9), we use tap water to represent the mildly corrosive solutions in the tank. The uncoated stainless steel tank bottom and the coating breaks/defects/holidays on the coated carbon steel ensues a cathode to anode area ratio of at least 300. GC-Compass predict that galvanic corrosion would perforate the wall thickness in 0.224 years (2.688 months)! Other galvanic corrosion prediction software based on the static "curve crossing" methodology simply fails to model this critical effect of cathode to anode area ratio on the galvanic corrosion rate and galvanic compatibility.
Figure 9 GC-Compass Predicts Galvanic Corrosion and the Effect of Cathode-to-Anode Area Ratio in Carbon Steel Storage Tank with SS304 Clad Bottom
Service Life Prediction of a Aluminum Casing of a Water Heater
A hospital needed an emergency power supply in case of mains failure, so a diesel engine was provided. To ensure that the diesel would cut in immediately the power failed, it was kept warm by means of a water heater with an aluminium casing. After a few months in operation, the 8 mm thick aluminium casing was penetrated causing the water to leak out. Inspection showed that a copper heating element had been used. Copper ions deposited at the 12 o'clock position by convection and caused extremely rapid pitting. In GC-Compass (Figure 10), the Al-Cu galvanic couple is selected and it predicted that the 8 mm thick Al casing would be perforated in 0.292 years (3.5 months). Other galvanic corrosion prediction software based on the static "curve crossing" methodology simply fails to model this critical effects of service temperature and cathode to anode area ratio on the galvanic corrosion rate and galvanic compatibility in tap water.
Figure 10 GC-Compass Predicts Pitting Corrosion Due to Galvanic Effect in Aluminium Casing
The powerful applications of GC-Compass are truly unlimited in engineering design, galvanic corrosion prediction and modeling, materials compatibility assessment, trouble-shooting process-related issues and failure analysis of components and systems.
Figure 11 shows the feature comparison between GC-Compass and other software based on curve-crossing methodology.
Figure 11 GC-Compass Offers More Features
Than Other Software Based on Curve-Crossing Methodology.
GC-Compass, giving you the right directions in Galvanic Corrosion Prediction and Assessment
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