Log in
Article search:

Q & A

microbial corrosion

whats the treatment for microbial corrosion on steel
i have good photos and description of it but any info would be very useful
thanks

Asked by: mb  | 10.09am, Friday 13 March


WW says:

Microbial corrosion of steel is a very real problem for pipeline operators but a lesser one for narrowboaters. It typically occurs more in nitrate rich waters which can include most of the canal system. The most common seems to be GALLIONELLA FERRUGINEA which forms little bright craters covered with a sort of orange pustule. This cleans off easily when pressure washed but the microbes will often still be present and can continue to corrode the steel even when painted over. A good paint covering will slow the microbial activity but will not entirely stop it; without any covering a ready supply of nutrient rich canal water will allow the microbes free rein.
Difficult to fully eradicate without grit blasting the steelwork but a decent pressure wash will clean the exposed metal and the good paintwork. Going over the obviously corroded and pitted areas with a bleach solution, working it in well with a stiff brush or using a hand sprayer, will be the best way to kill any remaining microbes. Be sure to wear protection.
As always, a decent paint film is the best way to protect the hull from corrosion whatever the cause.

Rupert Smedley  | 2.58PM, Friday 13 March

If using a bleach solution then domestic THIN bleach diluted 1:10 would give a solution of the appropriate free chlorine concentration- but may not remain in contact with the surface long enough to kill all microbes. The surface will also contaminate again fairly quickly unless good preparation and adhesion of the paint film is produced as Rupert says. There are commercial products available to deal with metal microbial contamination as well but aren't cheap...

Mark Langley  | 4.56PM, Friday 13 March

The action of dilution releases chlorine into solution in a form such that it can react/clean.

Rupert Smedley  | 11.50AM, Saturday 14 March

It's down to concentration not strength- in chemical terms the are not the same things. If you use too concentrated chlorine solutions it won't increase the effectiveness against microbes but will be more likely to damage to underlying metal. Cleaning off with an industrial jet wash with remove most of the material- then a repeated solution of dilute chlorine applied- rinsed off and then reapply paintwork properly is the best course of action. As Rupert says a good paint film is the most important. Cruising the boat rather than keeping it tied up in one place tends to improve underwater conditions.

Mark Langley  | 9.09AM, Sunday 15 March


Readers say:

thanks but i dont understand why to dilute the bleach when recommended diluted hypoclorite [15pc] is many times stronger.
what are the commercial products. thanks

mb  | 5.42PM, Friday 13 March

re: Mark Langley | 4.56PM, Friday 13 March
The action of dilution releases chlorine into solution in a form such that it can react/clean
========================do u know where i can study more to that effect [above]
thanks

mb  | 12.19PM, Saturday 14 March

thanks i will bear that in mind. would u care to look and comment on the in depth article on the Keel Black web site

mb  | 6.06PM, Sunday 15 March

thanks i will bear that in mind. would u care to look and comment on the in depth article on the Keel Black web site

mb  | 6.09PM, Sunday 15 March

pdf link is at bottom of page almost
https://www.keelblack.co.uk/

mb  | 6.10PM, Sunday 15 March

to address this [copied below] would several applications do the trick and how long before it re-contaminates , would this be hours , days or weeks, thanks for all the info
"but may not remain in contact with the surface long enough to kill all microbes. The surface will also contaminate again fairly quickly unless good preparation and adhesion of the paint film is produced"

mb  | 6.19PM, Sunday 15 March

You must log in to post an answer.