Effect of Turbulence on the Passive Film Growth and Associated Durability of Aluminum Alloys in Simulated Seawater

Turbulent fluid flow at high Reynolds numbers presents significant degradation risks to active-passive metals due to enhanced localized degradation phenomena. A multidisciplinary experiment was proposed to study the relationship between hydrodynamics in fully-developed pipe flow and both the growth and performance characteristics of passive films. Preliminary work was performed to set up (i) an environmental chamber for the experiment, (ii) design a custom wall shear stress sensor and constant temperature anemometer traverse system to monitor hydrodynamic conditions in-situ, (iii) monitor in-situ degradation through an array of ultrasonic thickness transducers, and (iv) acquire data and control the environment via a LabVIEW routine. A validation experiment was conducted on a 1220 mm long experimental section of 45.7 mm inner diameter AA2024-T3 tubing in simulated seawater. Extensive degradation was observed in-situ and confirmed with ex-situ techniques after sequential exposure to fully-developed turbulent flow at an expected wall shear stress of 10 Pa for 180ks (Reynolds number of 122,000) and then at 40 Pa for 630ks (Reynolds number of 262,000). No typical erosion-corrosion hydrological features were observed, however significant pitting and intergranular corrosion were observed with corrosion product caps covering 47% of the total ultrasonic transducers' measurement area. Passive film and pit growth were recorded via ultrasonic thickness measurements with an observed simultaneous decrease in dissolved oxygen content. The validation experiment successfully demonstrated the capability of the designed and constructed sensors for the proposed experiment. Numerous areas of suggested development and research were identified to ensure accuracy and improve interpretation of future experiments.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Materials Science and Engineering

Department dc:contributor.department

Materials Science and Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2018

Author dc:creator

• Todoroff, Peter Kent

Chair dc:contributor.committeechair

• Hendricks, Robert Wayne

Committee members dc:contributor.committeemember

• Schetz, Joseph A.
• Trueman, Elissa
• Corcoran, Sean G.

• tribocorrosion
• aluminum
• AA2024-T3
• Turbulence
• passive film
• corrosion loop
• erosion-corrosion
• pitting corrosion

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

vt_gsexam:15705

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/83770