When conducting corrosion testing of metals in hydrofluoric acid (HF) solutions, a suitable reference electrode choice would be the saturated calomel electrode (SCE), also known as the mercury/mercurous chloride electrode. Here's why:

1. Stability: The SCE is stable and reliable in a wide range of acidic solutions, including concentrated acids like hydrofluoric acid. It provides a stable reference potential over time, allowing for accurate and consistent measurements.

2. Compatibility: The SCE is compatible with most metallic materials commonly used in corrosion testing. It does not introduce any significant bias or interaction with the metal being tested, ensuring accurate corrosion measurements.

3. Reference Potential: The SCE has a well-defined and reproducible reference potential, which makes it suitable for comparing the corrosion potentials of metals in HF solutions. It provides a consistent reference point for measuring the electrochemical behavior of the metal.

When choosing a reference electrode for concentrated acidic solutions, such as HF, several factors should be considered:

1. Chemical Compatibility: The reference electrode should be chemically stable in the acidic solution and not react with the acid or any other components present. It should not introduce any contamination or interfere with the corrosion process.

2. Stability and Consistency: The reference electrode should maintain a stable and reproducible potential over time. This ensures accurate and reliable measurements throughout the corrosion testing period.

3. Electrochemical Potential Range: The reference electrode should have a potential range that is suitable for the expected range of potentials encountered during the corrosion testing. It should cover both the anodic and cathodic regions of the electrochemical behavior of the metal.

4. Material Compatibility: Consider the materials used in the reference electrode construction. Some materials may be incompatible with certain acidic solutions, leading to potential contamination or degradation.

Thank you so much Lamia Fatima but I believe the the Saturated calomel electrode would be reactive to HF. Ag/Agcl electrode would be more appropriate for HF reactions as Ag is an Nobel metal and less reactive than the mercury. What's your thoughts on this?

@Muhammad Junaid Anjum yes there is a possibility that HF can react with the mercury in the SCE and form mercury fluoride, which can alter the electrode potential and compromise the accuracy of measurements. And Ag/Agcl is more resistant to the corrosive effects of HF. So its way more better to go with the second option.

I suggest using a calomel or silver chloride electrode in a closed electrochemical key - preferably made of plastic.

stefan krakowiak

When testing the corrosion of metals in hydrofluoric acid, it's important to use a reference electrode that is compatible with the acid and does not interfere with the electrochemical measurements. In general, the most suitable reference electrode for this application is the silver/silver fluoride (Ag/AgF) electrode.

Ali Zeinodiny Thank you so much for your answer but I believe this reference electrode is not commercially available. Did you try this electrode before? if yes can you kindly share the link of manufacturers?

If you prepared it by yourself, what concentration of silver fluoride has been used and what was the impedance of the reference electrode and durability?

I suggest Ag/AgCl electrode