Chemistry-Structure-Property Interrelationships for Calcareous Deposits as Stand-Alone Coatings
Abstract
Experiments have been performed where 1018, A710, A537 and HY80 steel specimens of surface finish corresponding to 120, 320, 600 and 1500 polishing were polarized potentiostatically in seawater at -900 mv (SCE). The resulting calcareous deposits were analyzed with regard to structure, composition and morphology and found to be comprised of a relatively thin inner Magnesium rich layer which formed initially and a subsequent, thicker, outer aragonite precipitate. The effect of this dual deposit structure, as well as variations in substrate, surface finish and electrolyte flow rate, upon current density decay was evaluated; and the observed trends are discussed in terms of the film formation process and cathodic protection utility. Calcareous deposits are a relatively unique type of surface film comprised primarily of Calcium Carbonate and Magnesium Hydroxide which precipitate upon cathodic surfaces in seawater. This occurs as a consequence of increased pH near the metal-electrolyte interface. The importance of calcareous deposits to the effective, efficient operation of marine cathodic protection systems is generally recognized by engineers and scientists concerned with cathodic protection in submerged marine environments.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 07, 1989
- Accession Number
- ADA216031
Entities
People
- Samual W. Smith
- William H. Hartt
Organizations
- Florida Atlantic University