What is it about?

Adsorption and inhibition behavior of 1,2,3-benzotriazole (BTA) and 2,5-dimercapto-1,3,4-thiadiazole (DMTD) on brazing Cu-Ag alloy was studied in deionized water using potentiodynamic polarization measurement, adsorption isotherm investigation and X-ray photoelectron spectroscopy (XPS). Pure Ag and pure Cu were included to investigate the mere effect of each component on the alloy’s behavior. Results show better inhibition of DMTD for Ag and BTA for Cu, both by chemisorption. BTA was found to follow Langmuir isotherm while DMTD obeyed Temkin adsorption isotherm, despite both acting as a mixed type inhibitor. Combining the two inhibitors increased the inhibition efficiency over 80% for the Cu-Ag alloy. XPS spectra demonstrate the formation of DMTD protective film through DMTD’s functional groups of pyrrolic N from the azole ring and thiol S from the mercapto anchoring group on Ag and thiol S on Cu. Compared to BTA, the higher affinity of DMTD to Ag was attributed to the involvement of two heteroatoms with the Ag surface.

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Why is it important?

The eutectic Cu-Ag alloy is being utilized in cooling systems of data center facilities. In these deionized (DI) water-based systems, copper channels with copper fins brazed with Cu-Ag eutectic alloy are sandwiched between two copper plates and are affixed to thousands of central processing units (CPU). Draining the heat away from the CPUs is the objective of employing such systems. In spite of using benzotriazole (BTA) as an inhibitor, corrosion takes place leading to the detachment of copper fins from the brazing area. The reasoning behind choosing this inhibitor has been based on the fact that BTA protects copper well and Ag as a noble material would be intact. However, it turned out that the Ag rich phase is vulnerable in such conditions raising reliability and safety concerns.


In the present work, with the objective to lower the risk of corrosion as an essential threat to the safety of any system where Cu and Ag are in contact, adsorption isotherm studies derived from the electrochemical measurements were conducted. Subsequently, the adsorption mechanism of BTA and DMTD into these metals was explored. In addition, X-ray photoelectron spectroscopy (XPS) investigations further shed light on the reasons for the differences observed between the adsorption strength and inhibition behavior of each organic molecule and further backed on the requirement of combining the two inhibitors studied to achieve a higher corrosion protection. The overall objective was to identify inhibitors capable of providing corrosion protection of Cu, Ag and Cu-Ag alloys.

Hooman Rahmani
Texas A&M University College Station

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This page is a summary of: Corrosion Inhibition of Brazing Cu-Ag Alloy with 1,2,3-Benzotriazole and 2,5-Dimercapto-1,3,4-Thiadiazole, CORROSION, October 2020, NACE International, DOI: 10.5006/3642.
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