ABSTRACT
An investigation into the development of sheet steel groundcoat enamel from local raw materials was carried out. These local raw materials included: feldspar, quartz, magnesite, whiting, baryte and manganese dioxide. Several formulations were made. Of the five formulations that yielded best performance properties, enamel B had the highest local input of raw materials of 84 percent, followed closely by D with 78 percent, then A with 71.5 percent, C with 68 percent and finally E with 64 percent. Borax or boric acid constituted about 95 percent of the fore i gn input. The raw materials were smelted and fritted using the quenching method of fritting. Complete fusion of batch raw materials was attained after 1.5 - 3 hours. Enamel E had the lowest maturing temperature of 1080ÂC, followed by A with maturing temperature of 1115ÂC, C and D had 1150ÂC maturing temperature while B matured at 1200ÂC. The enamels were applied on low carbon sheet steel test pieces. Firing was carried out at 840ÂC - 880ÂC for 4 -12 minutes. Firing at the higher temperature range for shortertime yielded better performance properties than at lowertemperature range for longer time. The enameled samples were tested for fundamental performance properties. The coating thickness varied from 0.40mm - 0.48mm. When heated and quenched for eight successive temperatures of 170, 175, I8O, 185, 190, 195, 200 and 205ÂC, the enameled samples showed no signs of crazing, flaking off or cracking. When exposed to a 10 percent solution of citric acid for 15 minutes, enamels B, D and E showed no damage in appearance and relative cleanabi1ity while A and C failed this acid resistance test. There were no resultant damage to the enamel coating when subjected to impact test. The order of gloss and desired colour is: E > A > D > C > B When compared with industrial standands 11 and I2, all the formulations A, B, C, D, and E yielded successful performance properties but enamel E proved most successful.
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