X-ray diffraction and scanning electron microscopy studies of calcium carbonate electrodeposited on a steel surface

Abstract

Calcium carbonate was deposited on a stainless steel surface with the use of an electrical potential of 10 V. The crystals formed on the surface were examined with X-ray diffraction and with scanning electron microscopy, which revealed that calcite, vaterite and amorphous calcium carbonate was formed. Two different surface active polymers were added to the solution and their effect on the crystal structure was investigated. It was found that the more hydrophilic of the two polymers promoted calcite growth and suppressed vaterite growth. The more hydrophobic polymer completely inhibited vaterite growth. Both polymers decreased the amount of crystals formed on the steel surface, the more hydrophobic polymer being the most effective. The crystal inhibition efficiency was enhanced close to the cloud point of the polymers. The results were compared with the effect of poly(acrylic acid), a commonly used antiscalant. It was found that poly(acrylic acid) was about as efficient as the more hydrophobic polymer in decreasing the amount of calcium carbonate. At higher concentrations of poly(acrylic acid), almost all of the calcium carbonate precipitated in the amorphous form.