Rust staining

[Russell griffiths]

Morning. 

Im looking for something that I can use to neutralise some very minor rust staining. 

I have aluminium gutters that are powder coated on the outside but raw aluminium on the inside. Drilling some holes in steel I unfortunately let some steel swarf fall into the gutter, I swept it out but obviously missed tiny particles that have now rusted leaving thousands of tiny tiny orange dots on the inside of the gutter, it will probably have no ill effect but I would like to try and rub it off or neutralise it in some way. 

The dots rub off easily with a vigorous rub with my finger. 

 

Any thoughts. 

Cheers. Russ. 

[nod]

My son uses Kurust in his body shop Shifts anything 

[scottishjohn]

13 minutes ago, Russell griffiths said:

Morning. 

Im looking for something that I can use to neutralise some very minor rust staining. 

I have aluminium gutters that are powder coated on the outside but raw aluminium on the inside. Drilling some holes in steel I unfortunately let some steel swarf fall into the gutter, I swept it out but obviously missed tiny particles that have now rusted leaving thousands of tiny tiny orange dots on the inside of the gutter, it will probably have no ill effect but I would like to try and rub it off or neutralise it in some way. 

The dots rub off easily with a vigorous rub with my finger. 

 

Any thoughts. 

Cheers. Russ. 

used to get same problem when fitting after market glass sunroofs  if fitter did not cover entire roof with a sheet except for where the jigsaw would make its cut 

the small particles were hot when they landed on paint so burnt  into paint surface --so very hard to remove without rubbing 

Isuspect if it is upsetting you then rubbing will be best way

with maybe coarse "scotch brite pad"+ water 

-maybe the inside of gutter has a coating --like pure alluminium -that you cannot easily see to stop it corroding --so acid treatment sounds a bit agressive to me 

 

Edited February 17, 2020 by scottishjohn

[scottishjohn]

1 minute ago, nod said:

My son uses Kurust in his body shop Shifts anything 

that has a phosphoric acid base with lead --which turns most things black as it deposits the lead -thats how it stops rust by coating it with lead

[Russell griffiths]

It does come off with a rub of your finger so I did wonder about just using a dishwasher sponge and a little water in the gutter and go along and flush it all clean. 

[Jeremy Harris]

Phosphoric acid works by converting red ferric oxide (rust) into black ferric phosphate.  Nothing to do with lead, the black comes from the natural colour of ferric phosphate.  Ferric phosphate is a pretty good primer base on steel, as it will provide a degree of further corrosion protection, will readily absorb oil to provide further corrosion protection for "blacked" steel parts and bonds well to further paint coatings.

 

In this case, I'd be inclined to just wash out all the bits of rusty swarf and then just wipe away any staining if you can.  Phosphoric acid isn't a very strong acid, but if you can avoid using it I would.  If you do get phosphoric acid on particles of swarf it will probably make them more corrosion resistant for a time, but they will start to rust again before long.

[scottishjohn]

7 minutes ago, Jeremy Harris said:

Phosphoric acid works by converting red ferric oxide (rust) into black ferric phosphate.  Nothing to do with lead, the black comes from the natural colour of ferric phosphate.  Ferric phosphate is a pretty good primer base on steel, as it will provide a degree of further corrosion protection, will readily absorb oil to provide further corrosion protection for "blacked" steel parts and bonds well to further paint coatings.

 

In this case, I'd be inclined to just wash out all the bits of rusty swarf and then just wipe away any staining if you can.  Phosphoric acid isn't a very strong acid, but if you can avoid using it I would.  If you do get phosphoric acid on particles of swarf it will probably make them more corrosion resistant for a time, but they will start to rust again before long.

no argument with your post 

but kurust  has a high lead content--not just acid

the idea being everything else is converted as you say and it leaves a coating of lead on top of that as well

 and any acid on aluminium is best avoided

 correct primer for alloy sheet is an  etch primer to start with before actual real primer coats  --the acid in it makes a good bond for the actual primer coat --so acid and alloy--not my first choice ever

 

Edited February 17, 2020 by scottishjohn

[Jeremy Harris]

11 minutes ago, scottishjohn said:

no argument with your post 

but kurust  has a high lead content--not just acid

the idea being everything else is converted as you say and it leaves a coating of lead on top of that as well

 and any acid on aluminium is best avoided

 correct primer for alloy sheet is an  etch primer to start with before actual real primer coats  --the acid in it makes a good bond for the actual primer coat --so acid and alloy--not my first choice ever

 

 

 

No it doesn't, it's lead-free.  The MSDS is here: https://www.hammerite.co.uk/files/2017/02/HM_GB_EN_KURUST.pdf

 

 

[scottishjohn]

11 minutes ago, Jeremy Harris said:

 

 

No it doesn't, it's lead-free.  The MSDS is here: https://www.hammerite.co.uk/files/2017/02/HM_GB_EN_KURUST.pdf

 

 

then I,m out of date --no suprise there --it used to be -- maybe why it don,t work as well as it used to --it has been made for over 40 years anyway 

[Jeremy Harris]

1 minute ago, scottishjohn said:

then I,m out of date --no suprise there --it used to be -- maybe why it don,t work as well as it used to --it has been made for over 40 years anyway 

 

 

The MSDS doesn't list everything, only the hazardous stuff, and IIRC Kurust uses tannic acid, rather than phosphoric acid, as the ferric oxide converter.  Both tannic acid and phosphoric acid are used in food (phosphoric acid is what give Coke much of its flavour, for example), so they don't normally need to be listed as hazardous.