| Research Abstract |
Using rusted iron disks pressed artificially, effects of fluorinated oligomers added to alkaline solutions on removal of salt were investigated. As a result, addition of fluorinated oligomer to KOH solution was found to bring improvement on removal of salt compared with the sesquicarbonate solution that have been applied in practice. Also, we found that betaine-type oligomers are adapted for removal of salt. To find which type of betaine is adequate for this purpose, we investigated the effects of fluorinated oligomers on removal of salt experimetally.
Amount of salt removed for KOH aqueous solution containing SK-6, betaine-type oligomer with hydrophilic group and long chains of fluorinated group, increased 3.7 times as much as that for the sesquicarbonate solution. On the other hand, an oligomer, SK-15, with hydrophobic group was found to prevent the iron disk from rusting.
Next, we investigated the effects of the oligomers on long-term conservation of iron artifacts treated by alkaline
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solutions containing betaine-type fluorinated oligomers. We used test pieces which had been kept in our romm for 14 to 18 months. Then, the test piece was suspended in a 100 mL bottle with water on the bottom, which was kept in air to prevent from contacting with water. After that, change in weight was measured. From the results, we found that increments of dry weight of the test pieces were 5.9 times for sesquicarbonate, 2.5 times for SK-15, 2.2 times for SK-2, 1.3 times for SK-6 compared to that for KOH solution without oligomers. The increment in weight due to re-rusting decreased with increasing the amount of salt removed.
Consequently, we found that re-rusting in a short period after removal treatment of salt by alkaline solution containing fluorinated oligomer was suppressed by the hydrophobic group in the betaine-type oligomer, and re-rusting in long-term conservation will depend on the amount of salt remainted in the iron artifacts. Hence, the SK-6 is considered to be adequate as an additive to alkaline solution for removal of salt, because in our experiment addition of the SK-6 most improved the removal of salt. Less
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