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Predicting Atmospheric Galvanic Corrosion Of Aluminum Alloy By Combining Electrochemical Techniques And Accelerated Laboratory Corrosion Tests

Predicting Atmospheric Galvanic Corrosion of Aluminum using Accelerated Laboratory Electrochemical Experiments
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Aluminum (Al) alloys are the most common non-ferrous metals used (approximately 25 million tons per year) and the second most commonly used metal alloy after steel1. Some of the properties of Al alloys that attribute to their worldwide use include lightness, thermal conductivity, electrical conductivity, suitability for surface treatments, and corrosion resistance. Al alloys are also combined with other metals/materials to achieve desired properties for specific applications. Al alloys can be joined to other materials with ease to enhance their combined properties with the following techniques: welding, bolting, riveting, clinching, adhesive bonding, and brazing1. 

Product Number: 51322-18163-SG
Author: Raghu Srinivasan, Toomas Kollo, Matt Cullin
Publication Date: 2022
Industry: Corrosion Monitoring and Control
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$20.00
$20.00

Aluminum (Al) alloys are the most commonly used non-ferrous metals (approximately 25 million tons per year) for various technical applications and the second most commonly used metal alloy after steel. Al alloys are also combined with other metals/materials to get specific desirable properties for particular applications. However, a system of dissimilar materials can lead to potential corrosion problems such as galvanic and/or crevice corrosion. In this work, atmospheric galvanic corrosion of aluminum (Al) alloy was predicted by combining electrochemical techniques and accelerated laboratory corrosion tests. Three different galvanic couples were analyzed where 6061-T6 Al alloy (UNS A96061) was coupled with a passivating metal (304 stainless steel or UNS S30400), noble metal (copper or UNS C11000) and a conductive polymer matrix composite (PMC) reinforced with carbon fiber. The galvanic current flowing between the anode and cathode was measured using the zero-resistance ammeter (ZRA) technique in the humidity-chamber setup. Electrolytes with varying amounts of chloride contents were used to imitate different atmospheric conditions. An equation based on Faraday’s law was developed to calculate the corrosion rate in grams per meter square per day (gmd) by relating the time of wetness (TOW) from the field exposure to the galvanic current measured from the accelerated laboratory experiments. The total exposure time was divided into wet periods (Twet) and dry periods (Tdry). Cyclic corrosion test chamber following a modified GM9540P cycle and outdoor exposure experiments are planned for the future.  

Aluminum (Al) alloys are the most commonly used non-ferrous metals (approximately 25 million tons per year) for various technical applications and the second most commonly used metal alloy after steel. Al alloys are also combined with other metals/materials to get specific desirable properties for particular applications. However, a system of dissimilar materials can lead to potential corrosion problems such as galvanic and/or crevice corrosion. In this work, atmospheric galvanic corrosion of aluminum (Al) alloy was predicted by combining electrochemical techniques and accelerated laboratory corrosion tests. Three different galvanic couples were analyzed where 6061-T6 Al alloy (UNS A96061) was coupled with a passivating metal (304 stainless steel or UNS S30400), noble metal (copper or UNS C11000) and a conductive polymer matrix composite (PMC) reinforced with carbon fiber. The galvanic current flowing between the anode and cathode was measured using the zero-resistance ammeter (ZRA) technique in the humidity-chamber setup. Electrolytes with varying amounts of chloride contents were used to imitate different atmospheric conditions. An equation based on Faraday’s law was developed to calculate the corrosion rate in grams per meter square per day (gmd) by relating the time of wetness (TOW) from the field exposure to the galvanic current measured from the accelerated laboratory experiments. The total exposure time was divided into wet periods (Twet) and dry periods (Tdry). Cyclic corrosion test chamber following a modified GM9540P cycle and outdoor exposure experiments are planned for the future.  

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