Painting the Forth Bridge

Materials World magazine
,
1 Apr 2008

‘I heard him then, for I had just
Completed my design
To keep the Menai Bridge from rust
By boiling it in wine.'

Lewis Carroll, ‘The White Knight's Song'.

A news item can have an impact which is not related to the intrinsic importance of the issue - it also depends on the mood of the time, the zeitgeist.

Furore surrounding Forth Bridge

In 1993 when British Rail, then owners of the steel Forth Bridge in Scotland, UK, announced that it was short of cash and would save money by interrupting the ‘normal', almost continuous, painting of the bridge, it stimulated a storm of protest. British Rail's critics feared that accelerated rusting would render the span useless. These concerns were expressed in an impassioned article in the Independent on Sunday by its then Editor Ian Jack. Tam Dalyell MP raised the matter in the House of Commons and other Scottish MPs supported his concerns. The Prince of Wales was alerted and brought forward his planned visit to the bridge. He asked to be kept informed on the issue.

I was peripherally involved. Jack had asked me to represent him on an inspection of the bridge as a guest (with other interested parties) of Railtrack. Unfortunately, the visit in February 1995 coincided with a long-planned trip to India (to discuss, among other things, the corrosion of the Taj Mahal!). Stuart Lyon, a corrosion expert from the former UMIST, took my place. He reported that, while the bridge looked bad, the faults were mostly cosmetic. In due course the furore died down.

Muted reaction to longer-lasting paint

The Forth Bridge remained on the backburner until a few weeks ago when Iain Coucher, Chief Executive of Network Rail, announced that when the current painting is completed in 2012, repainting would not be required for at least another 25, possibly 40, years. This was due in part to the remarkable properties of a new paint.

In contrast to the reaction over a decade earlier, the news prompted little media interest. Evidently there now existed a different zeitgeist. All I have found are two whimsical pieces by Tim Dowling and Giles Smith in The Guardian and The Times, respectively. Both confined their complaint to the destruction of the much used similie- ‘it's like painting the Forth Bridge' implying a never-ending task (This arose from the inaccurate belief that painting the Forth Bridge was a Sisyphean undertaking - as soon as one painting campaign was completed it was time to start another).

Lifespan of concrete and steel bridges

If the new paintwork can indeed protect the bridge for 40 years then only one more entire repainting will be needed (in about 2050) before the bridge's bi-century in 2090. Such longevity contrasts sharply with the lifespan of many modern concrete bridges.

In 1964 the Queen opened the Forth Road Bridge, a largely concrete structure alongside the Forth Railway Bridge. Today it is already in poor condition. Its steel cables are badly corroded, and, according to the redoubtable Jack, the cost of replacing them would be about 100 times the bridge's original price of £17m. If the cables are not replaced, the bridge will have to be closed sometime between 2013-19.

How can a concrete bridge completed in 1964 have a lifespan of only 50 years whereas a steel bridge constructed on virtually the same site, but finished in 1890, has a lifespan of over 200 years? Perhaps a reader of Materials World can explain.

 

Further information:

Tam Dalyell MP comments on the Forth Bridge
Network Rail's announcement regarding painting the Bridge
'Wanted: a new idiom to replace the Forth Bridge', Tim Dowling, The Guardian, 20 February 2008
'Sisyphus, but with brushes', Giles Smith, The Independent, 20 February 2008