Evaluation of pitting corrosion by dynamic speckle pattern analysis.

Area of Science:

• Materials Science
• Corrosion Engineering
• Optical Metrology

Background:

• Increasing demand for non-destructive, real-time, high-resolution methods in metal corrosion studies.
• Pitting corrosion, a localized form of metal degradation, can lead to structural failure.
• Need for cost-effective and easily implementable techniques for quantitative corrosion evaluation.

Purpose of the Study:

• To propose and validate the dynamic speckle pattern method for quantitative evaluation of pitting corrosion.
• To assess the feasibility of this optical technique as a quasi in-situ method.
• To analyze the corrosion behavior of Custom 450 stainless steel in a saline environment.

Main Methods:

• Utilizing a He-Ne laser to illuminate a Custom 450 stainless steel sample immersed in 3.5 wt% NaCl solution.
• Applying a specific potential to initiate pitting corrosion.
• Analyzing changes in time-integrated speckle patterns generated by laser light scattering to monitor corrosion evolution.

Main Results:

• The dynamic speckle pattern method provides a quantitative approach to evaluate pitting corrosion.
• Observed changes in speckle patterns correlate with the progression of corrosion.
• Analysis indicates a decreasing growth rate of pitting corrosion over time.

Conclusions:

• The dynamic speckle pattern method is a viable, low-cost, quasi in-situ optical technique for pitting corrosion assessment.
• This method offers a practical alternative for real-time corrosion monitoring.
• The study demonstrates a characteristic decrease in pitting corrosion growth rate over time for the tested material.