Scale and Corrosion Prevention in Cooling Water Systems Part II: Calcium Sulphate
This paper describes an experimental study on calcium sulphate scaling and prevention by newly treated poly- acrylamide in a laboratory model. In order to study the inhibiting capacity of the chemical used, experiments were per- formed in solutions involving treatment of synthetic sea water with different concentrations of the polymer. Polyacryla- mide gave significantly lower precipitation rate compared to the treatment in absence of inhibitor. The inhibitor probably is adsorbed on the active growth sites of the initially formed crystals. The performances of scale inhibitor with different concentrations were analyzed in terms of the amount of soluble calcium ions in solution. The results showed that the amount of scale was reduced to 0.00%, with, 10-15 ppm polymer additions, after 1 day incubation at 90°C. Antiscale agents specific to calcium sulphate deposits have recently been developed and tested on a laboratory scale. The work was also extended to study the corrosion inhibition of polyacrylamide to both C-steel and copper specimens in contact with synthetic cooling water environment. Electrochemical polarization techniques reveal that the inhibitor acts as anodic type with respect to C-steel and mixed type for copper. Corrosion current jcorr and corrosion rate CR were reduced and inhibi- tion efficiency IE% increases with polymer additions. The inhibition effects are due to the formation of protective film. Morphological investigation for CaSO4. 2H2O gypsum crystals formed in synthetic sea water indicate reduction of cal- cium sulphate crystals in the presence of the polymer as indicated by scanning electron microscopic (SEM) studies.
Development of anti-scale poly(aspartic acid–citric acid) dual polymer systems for water treatment
The formation of calcium sulphate and calcium carbonate scale poses major problems in heat exchangers and water cooling systems, thereby affecting the performance of these types of equipment. In order to inhibit these scale formations, new types of biodegradable water soluble single polymer and dual poly(aspartic acid–citric acid) polymers were developed and tested. The effectiveness of single polymer and four different compositions of poly aspartic acid and citric acid dual polymer systems as scale inhibitors were evaluated. Details of the synthesis, thermal stability, scale inhibition and the morphological characterization of single and dual polymers are presented in this scientific paper. It was found that the calcium sulphate scale inhibition rate was in the range 76.06–91.45%, while the calcium carbonate scale inhibition rate observed was in the range 23.37–30.0% at 65–70 °C. The finding suggests that the water soluble dual polymers are very effective in sulphate scale inhibition in comparison of calcium carbonate scale inhibition.
Composite monolayer fabrication by an arc-spray process
A single layer (monotape) technique for fabricating complex high-temperature tungsten-fiber-reinforced superalloy composites is proposed. The fabrication of sheets of arc-sprayed monotape 38 cm wide and 122 cm long has been demonstrated. Composites fabricated using the method are shown to have equal tensile strength and a cleaner matrix than composites fabricated from powder metal cloth monotapes, and the present technique is less expensive than the powder metal fabrication techniques.