Thermally sprayed aluminum (TSA) has been used to protect offshore structures for decades. Their effectiveness in mitigating corrosion of steel structures in seawater has been demonstrated over the years. However, very little work is reported on the corrosion performance of TSA when damaged. Furthermore, data on the performance of damaged TSA in deep sea is virtually non-existent. To address these knowledge gaps, Al was sprayed onto carbon steel and defect (holiday) amounting to 3% of the sample area was drilled to expose the underlying carbon steel substrate. The sample was exposed to synthetic seawater at 5°C in an autoclave at 50 MPa to simulate 5000 m of water pressure for 90 days. After testing, examination of the sample revealed the formation of calcareous deposit on the exposed steel surface with no visible steel corrosion product. Detailed microstructural characterization of the calcareous deposit confirmed the formation of protective Mg-and Ca-containing layers. Thus, one can conclude that TSA has the potential to protect carbon steel in deep sea environment even when damaged.

Subject
Holidays, Steel surfaces, Marine environments, Corrosion rate, Aluminum, Synthetic seawater, Seawater, Scale formation, Steel, Carbon steel, Corrosion protection, Deposit corrosion, Calcareous deposits
Keywords:
TSA, calcareous deposit, thermal spray coatings, deep sea, marine corrosion
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2017
Association for Materials Protection and Performance (AMPP)
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