Unveiling Etching Dynamics with QCM-D: The Power of Time-resolved Analysis

Surface etching is a frequent challenge in cleaning and processing, often resulting in unwanted material loss or surface damage. Gaining a clear understanding of how and why etching occurs is essential for optimizing cleaning protocols and protecting valuable surfaces. In this post, we demonstrate how QCM-D (Quartz Crystal Microbalance with Dissipation monitoring) analysis can reveal the real-time dynamics of etching, providing actionable insights to help control and minimize surface damage.

Assessing surface etching: How QCM-D analysis can help optimize cleaning conditions

Undesired surface etching or corrosion can occur during cleaning, especially at high pH levels. To optimize cleaning protocols and achieve the desired degree of etching, it is important to assess how etching progresses over time and under different process conditions. QSense QCM-D offers time-resolved measurements, enabling detailed analysis of etching as a function of variables like temperature and pH.

With QCM-D data, you can extract valuable information, such as:

• Etching capacity: What is the etch rate under specific conditions (e.g., temperature X, pH Y)?
• Etching dynamics: How does the etching process evolve over time?
• Optimal conditions: Are there temperature “sweet spots” where etching is minimal but cleaning remains effective?
• Etch protector evaluation: Does a particular component protect the surface from etching?

Case example: How much does full formulation A etch a glass surface as a function of time at various temperatures?

To showcase the capabilities of QCM-D in assessing surface etching, we conducted an experiment analyzing how a full cleaning formulation etched a soda-lime glass surface across a temperature range of 15–55 °C. We also examined the distinct slow and fast phases of etching at each temperature.

Surface etching results: Insights from QCM-D measurements

The QCM-D frequency response, which directly reflects surface mass loss, reveals how temperature affects the etching process (see Fig. 1):

• Low temperatures (15, 25, and 35 °C): Etching proceeds slowly, with a gradual increase in frequency change (Δf).
• Higher temperatures: Etching rates increase, and a two-phase behavior emerges. The second phase is significantly faster, suggesting that elevated temperatures accelerate chemical reactions and alter etching dynamics.
• Beyond a specific threshold at 45 °C and 55 °C: Material removal becomes so extensive that it disrupts the sensor’s surface, potentially causing water entrapment and a sharp decrease in Δf.

Figure 1. Etching behavior of a soda-lime glass sensor exposed to a full formulation. Frequency shifts, Δf₃, at different temperatures during exposure to the market-ready formulation.

The slope of the frequency change (Δf) provides insight into the kinetics of the etching process. By analyzing how this slope varies with temperature (see Fig. 2), we can deduce reaction rates and better understand the mechanisms of material removal:

• Below 45 °C: A single, slow etching phase is observed, with low slope values.
• Above 45 °C: The slope increases sharply, indicating a transition to a fast-etching phase with rapid material removal.

Figure 2. Etching rates in the slow and fast phases. Data collected at 15 °C, 25 °C, 35 °C, 45 °C and 55 °C.

Key Takeaways: What the QCM-D analysis revealed

• The etching rates and dynamics are significantly influenced by temperature.
• At low temperatures (15-35°C): Etching proceeds slowly with a gradual increase in frequency change.
• At higher temperatures (above 35°C): Etching rates accelerate, showing a two-phase behavior with a notably faster second phase.

Concluding remarks: Advancing surface etching analysis with QCM-D

In this post, we demonstrated how QCM-D technology can deliver valuable, time-resolved insights into the dynamics of surface etching under a variety of conditions. By analyzing the interaction between a full formulation and a soda-lime glass surface across a temperature range of 15–55 °C, we found that both the rate and nature of etching are strongly influenced by temperature. At lower temperatures, etching occurs gradually, with a slow and steady increase in frequency change. In contrast, higher temperatures accelerate the process and reveal a distinct two-phase behavior, where the second phase is notably faster. This indicates that elevated temperatures enhance chemical reactions, fundamentally altering the etching dynamics.

These findings underscore the importance of understanding etching kinetics and the role of temperature—knowledge that is essential for optimizing cleaning processes and developing effective etch protectors to minimize undesired surface damage.

Download the technical white paper to learn more about this case study and other practical applications of QCM-D in cleaning analysis.