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Collection, Preservation and Display of Old Lawn Mowers

Rusty fuel tanks


I have a Qualcast 16 with a rusty fuel tank. Does anyone know of any companies who refurbish fuel tanks. Or have any suggestions of chemicals or techniques to clean the flaking rust inside he tank.

The tank is sound but full of flaking rust, I have seen some chemicals on the interest an some utube videos using pool cleaning acids etc.

I have heard you can use electrolis but not sure where I could purchase the equipment.

Any help or advice would be great.



wristpin Fri, 27/09/2019

There are various methods available for home de-rusting , mechanical, chemical rust converter, electrolysis and sealant - or a combination of these.

If the inside of the tank is heavily rusted start by trying to remove the worst by adding a cup of diesel or kerosene ( or even water) and then a handful of sharp gravel or even nuts and bolts. Then replacing the top and then giving it a vigorous shaking for several minutes . Repeat this treatment until it appears that all the loose rust has been removed.

The remaining rust may then be "killed" / converted by adding a proprietary rust converter and sloshing it around to reach all the inside walls of the tank. Alternatively any remaining rust may be removed by electrolysis which needs nothing more than some washing soda and a battery charger. Google electrolytic rust removal but note that most article concern hanging a rusty  item in a tank to clean it but you need to reverse the process to clean the inside of the tank and transfer the rust to the electrode.  

Be aware that some tanks have soldered joints around tap bosses or the threaded boss for the tank cap and the use of some aggressive rust removers such as " brick cleaning acid" may attack the solder.

Larger scale! A 14" grass box in a 205 litre tank

This may be useful



Chris G Mon, 30/09/2019

I've been in the chemical removal camp for many tanks & many years, how do you find the reoccurrence of rusting without a chemical or sealing application after? 

If submerged in decent fuel I'm sure it would be ok. Once empty and dried out properly, does the electrolysis process abate the rust coming back?

Series3boy Mon, 30/09/2019

Thank you again 

Have you got any recommendations on acids to use? Or a sealer once I have the tank clean. I notice that 2 stroke tanks that have sat for many years are rusty inside maybe there is something in two stroke oil that causes this.

wristpin Mon, 30/09/2019

My own experience is that electrolysis appears to leave a fairly inert surface but for long term storage I brim tanks with diesel or kerosene and seal the breather hole. For machines in regular use I brim the tank with whatever fuel the machine runs on at the end of the working period and seal the breather . In both cases the objective is to displace and then excluded moist air. I know that to some extent modern ethanol adulterated fuels are hygroscopic but starting with fresh fuel and excluding moist air seems to be as effective , if not more so, as adding additives.


Chris G Mon, 30/09/2019

Yes agree that mildly hygroscopic modern fuels should have little steel oxidising effect if brimmed, sealed and only left for a year or so or maybe ages?

The chemical process I’ve used in the past with hydrochloric as that active agent at varying concentrates does a great job at removing rust but it is quite aggressive at higher concentrates and also flash rusts quite quickly unless neutralised.


Had my fair share of restoring tanks with woeful over seal products which are nigh on impossible to get back to bear steel but yet have flacked badly causing all sorts of issues.

The only coating I would trust is the massively expensive and assiduously instructed POR – ultimately it is a coating, but it’s not failed on me yet in 10 years+ of tanks. Way over the top for small mower tanks perhaps..


Empty fuel tanks might be best stored in the Atacama J


Re questions on acids and sealer, my opinions only, above.

I’m no expert but I would think 2 stroke oil additive would help rather than make worse the effects of rusting, but they would still separate out with water being heavier and sitting at the bottom of the tank


Have you got some pics of this tank internally?