Transcript of the video "Time-lapse Photography of Galvanic Corrosion on an Iron Nail"
Length of video: 00:00:27
No narration during this video.
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At the beginning of the video, two nails sit in separate dishes side by side. Each nail is covered with a solution of agar, potassium ferricyanide and phenolphthalein. The nail on the left is wrapped with brass foil. The time-lapse video shows the two nails over an eight-hour period with photographs taken at two-minute intervals. The first photograph was taken two minutes after the solution was poured over the samples. There is a slight delay at the beginning of the video to allow the viewer to see the initial change at two minutes.
First, small areas of blue form at the bottom tip and the head of the nails and small areas of pink form over the brass and on the shaft of the nail on the right. The blue colour is from the reaction of potassium ferricyanide with iron ions produced by the corrosion of the nail. The pink colour is from the reaction of phenolphthalein with hydroxyl ions, which forms as dissolved oxygen is reduced. Over time, the pink and blue colours become more intense. After eight hours, the nail on the left has large dark blue haloes surrounding the tip and the head, and the surface of the brass is covered in dark pink. The nail on the right has a small dark blue halo around the head of the nail and a small dark pink halo along most of the shaft and the tip of the nail. The video shows that corrosion happens faster when iron is in contact with brass (galvanic corrosion of iron), as is the case with the nail on the left as compared to corrosion of the iron nail on its own on the right.
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This video was created by the Canadian Conservation Institute and is part of the Understanding galvanic corrosion learning resource.