Modeling localized corrosion in biofuel storage tanks

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Atmospheric storage tanks are susceptible to localized "pitting" corrosion.
• Biofuels, containing organic acids, may exacerbate corrosion compared to conventional fuels.
• Understanding corrosion mechanisms is crucial for tank integrity and environmental safety.

Purpose of the Study:

• To model the influence of biofuels on pitting corrosion in carbon steel storage tanks.
• To develop an electro-chemical phase-field model incorporating organic acid reactions.
• To predict corrosion rates and pit evolution for single and multiple interacting pits.

Main Methods:

• Developed an electro-chemical phase-field model.
• Numerically integrated nonlinear coupled partial differential equations using finite element methods.
• Tracked metal/electrolyte interface evolution and predicted corrosion rates.
• Validated single pit model against experimental data.

Main Results:

• Organic acids in biofuels significantly increase corrosion rates compared to conventional fuels.
• Corrosion rate follows a two-stage process, with pit depth described by a double power law.
• Multiple interacting pits show amplified corrosivity, with pit density being more critical than spacing.
• Observed "band" behavior in long-term pit growth for multiple pits.

Conclusions:

• The proposed model accurately predicts biofuel-induced pitting corrosion.
• Biofuels pose a higher corrosion risk, necessitating optimized maintenance and inspection strategies.
• The model serves as a tool for risk assessment and environmental hazard prediction.