Funkey,

I agree with your comment of  stainless steel for the bridges. Nace came out with a study regarding stainless for bridges which I posted a while back.

link was this:

https://www.nace.org/uploadedFiles/Corrosion_Central/Corrosion_101/White_Papers/CorrosionControlPlanForBridges.pdf

Another study to look at by Nace regarding the cost of Corrosion is this one:

http://impact.nace.org/documents/Nace-International-Report.pdf

the global cost of corrosion is estimated to be 2.5 trillion dollars, 3.4% of Global GDP

I read another study 

Corrosion will cost the US economy over $1.1 trillion in 2016

http://www.g2mtlabs.com/corrosion/cost-of-corrosion/

It is not just the cost of repair but the horrendous cost to human life. Bridges collapsing...plus other accidents like this one in Augustt of this year at an Ohio State Fair.

One person killed and several injured due to corrosion.

https://www.cbsnews.com/news/ohio-state-fair-accident-caused-by-ride-corrosion/

https://www.nace.org/60-minutes-missed-important-solution-to-infrastructure-woes-corrosion-control.aspx

There are 70,000 structurally-deficient U.S. bridges; most are still in use well past their design life, and more than 15 percent are at risk of catastrophic, corrosion-related failure.

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Building it right in the first place by using stainless for something this is planned to be around for a long time, saves money and lives.