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TWI comes up to scratch

Connect, January/February 1999


Angel Train Contracts - one of the three companies who own Britain's trains - consulted TWI recently looking for a method of repairing railway carriage windows.

The toughened glass windows get scratched or damaged, either accidentally by jewellery or deliberately by vandals. Every carriage has 20 windows, each held by 120 rivets. At the moment there is no way to repair the damaged panes so they have to be removed and replaced.

Angel Train Contracts were looking for a repair system that is cost effective, easy to apply and would fill the cracks so they could not be seen after treatment. The Advanced Materials and Processes Department at TWI thought that a sol-gel coating system might be the answer.

A glass coating system was chosen and, after some trials, the solution was applied across the entire window giving a tough surface with no cracks visible to the naked eye.

Until now, typical coating applications for sol-gel were 1-2 microns thick. However, TWI successfully applied a coating, which filled scratches of half a millimetre wide and 50 microns deep - the first time this had been attempted.

The trials were carried out on a horizontal surface and the next stage of tests aims to refine the coating so it can be applied vertically and ultimately be used on the windows in-situ thus saving both time and money.

For more information on sol-gel applications, contact Alan Taylor in the Advanced Materials and Processes Department. E-mail:

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