WotEver Posted May 9, 2019 Report Share Posted May 9, 2019 I’m cleaning some rusty parts in 45% Phosphoric Acid. When I remove them I’ll have a brown sludge at the bottom of the container. If I decant the more-or-less clear liquid and chuck the sludge will I have ‘active’ phosphoric acid, something somewhat less active, or something else entirely? Thanks in advance. Oh... and do I have to neutralise the steel/iron or can I just rinse it thoroughly? Link to comment Share on other sites More sharing options...
Machpoint005 Posted May 9, 2019 Report Share Posted May 9, 2019 Phosphoric acid works by converting iron oxide into iron phosphate. The brown sludge will contain phosphates, which can only have come from the phosphoric acid. The acid will therefore now be in a lower concentration but I can't tell you how low. It might well contain other substances to0. Link to comment Share on other sites More sharing options...
Boater Sam Posted May 9, 2019 Report Share Posted May 9, 2019 (edited) The effective strength will go down with use, the acid converts rust, ferrous oxide to iron phosphate, sludge. The solution will effectively be diluted. Thorough rinsing should be fine, the instructions for rust cures containing phosphoric acid, Jenolite, etc. just say wash well. The rusty parts will be black. Beaten to the post, that's why I don't back horses. Edited May 9, 2019 by Boater Sam Link to comment Share on other sites More sharing options...
WotEver Posted May 9, 2019 Author Report Share Posted May 9, 2019 Okay, thanks both, as I suspected Link to comment Share on other sites More sharing options...
tree monkey Posted May 9, 2019 Report Share Posted May 9, 2019 1 hour ago, WotEver said: Okay, thanks both, as I suspected Now the technical question is answered I tend to brush any waste onto bits of less vital metal work, for example I have a few Jerry cans that had small rust spots, brushed out the vactan, followed by primer etc from the same paint job Link to comment Share on other sites More sharing options...
bizzard Posted May 9, 2019 Report Share Posted May 9, 2019 1 minute ago, tree monkey said: Now the technical question is answered I tend to brush any waste onto bits of less vital metal work, for example I have a few Jerry cans that had small rust spots, brushed out the vactan, followed by primer etc from the same paint job Chinese jelly can no prenty lust. Link to comment Share on other sites More sharing options...
WotEver Posted May 9, 2019 Author Report Share Posted May 9, 2019 2 hours ago, tree monkey said: Now the technical question is answered I tend to brush any waste onto bits of less vital metal work, for example I have a few Jerry cans that had small rust spots, brushed out the vactan, followed by primer etc from the same paint job Well, I’ll have plenty of waste... using 10 litres at present and it’s only just enough to cover all the items. Link to comment Share on other sites More sharing options...
Cheshire cat Posted May 9, 2019 Report Share Posted May 9, 2019 Wow. It's pretty nasty stuff. It discolours paint If anyone is wondering there is a place in Lymm that does it on ebay through the post Link to comment Share on other sites More sharing options...
Dr Bob Posted May 10, 2019 Report Share Posted May 10, 2019 12 hours ago, WotEver said: Well, I’ll have plenty of waste... using 10 litres at present and it’s only just enough to cover all the items. I would guess the actual weight of rust you are converting is not that high so the depletion in phosphate ions will not be that great even when considering the larger phosphate ion. I would doubt you are weakening the acid strength that much. I could calculate it but my head might hurt and it would only be useful if we knew the weight of rust removed. Link to comment Share on other sites More sharing options...
WotEver Posted May 10, 2019 Author Report Share Posted May 10, 2019 4 minutes ago, Dr Bob said: I would guess the actual weight of rust you are converting is not that high so the depletion in phosphate ions will not be that great even when considering the larger phosphate ion. I would doubt you are weakening the acid strength that much. I could calculate it but my head might hurt and it would only be useful if we knew the weight of rust removed. Thanks. I have a scummy froth on the top at present. I’ll scrub the items later and see the best way to recover the acid. Would I be ok filtering it through a strong paper towel? Link to comment Share on other sites More sharing options...
Dr Bob Posted May 10, 2019 Report Share Posted May 10, 2019 1 hour ago, WotEver said: Thanks. I have a scummy froth on the top at present. I’ll scrub the items later and see the best way to recover the acid. Would I be ok filtering it through a strong paper towel? Probably.....if you need to? Maybe just scoop off the frothy top and decant the clear liquid. The Iron III oxide that is formed in the reaction should settle to the bottom of the liquid. If you are using the liquid just to remove rust then it wont matter if there is still some rust contamination in it. I dont think it is an equilibrium reaction so the presence of any iron III oxide or Iron phosphate will not slow it down. If you want to filter through paper then yes that will work ......but just be a bit messy. Messy didnt have a good game on Wednesday ...did he? Co'mon you Reds. Link to comment Share on other sites More sharing options...
WotEver Posted May 10, 2019 Author Report Share Posted May 10, 2019 25 minutes ago, Dr Bob said: Probably.....if you need to? Maybe just scoop off the frothy top and decant the clear liquid. The Iron III oxide that is formed in the reaction should settle to the bottom of the liquid. If you are using the liquid just to remove rust then it wont matter if there is still some rust contamination in it. I dont think it is an equilibrium reaction so the presence of any iron III oxide or Iron phosphate will not slow it down. If you want to filter through paper then yes that will work ......but just be a bit messy. Messy didnt have a good game on Wednesday ...did he? Co'mon you Reds. Thanks again. I’ll just decant it as is then, leaving behind as much sludge as I can and use that to spread around next-door’s huge tree... (did I just say that out loud?) 1 Link to comment Share on other sites More sharing options...
Dr Bob Posted May 10, 2019 Report Share Posted May 10, 2019 27 minutes ago, WotEver said: Thanks again. I’ll just decant it as is then, leaving behind as much sludge as I can and use that to spread around next-door’s huge tree... (did I just say that out loud?) Flush it down the loo. Phosphoric acid is good for cleaning toilets. We used to do it all the time on our lumpy water boat.......putting Coke down the toilet (the one you can buy in bottles, not the stuff you buy in the little bags) as Coke is essentially dilute phosphoric acid. Link to comment Share on other sites More sharing options...
WotEver Posted May 10, 2019 Author Report Share Posted May 10, 2019 5 minutes ago, Dr Bob said: Flush it down the loo. Does it dissolve limescale? Link to comment Share on other sites More sharing options...
tree monkey Posted May 10, 2019 Report Share Posted May 10, 2019 35 minutes ago, WotEver said: Thanks again. I’ll just decant it as is then, leaving behind as much sludge as I can and use that to spread around next-door’s huge tree... (did I just say that out loud?) Oy 1 Link to comment Share on other sites More sharing options...
Sapphal Posted May 10, 2019 Report Share Posted May 10, 2019 14 minutes ago, WotEver said: Does it dissolve limescale? Yes 1 Link to comment Share on other sites More sharing options...
cuthound Posted May 10, 2019 Report Share Posted May 10, 2019 2 hours ago, WotEver said: Thanks again. I’ll just decant it as is then, leaving behind as much sludge as I can and use that to spread around next-door’s huge tree... (did I just say that out loud?) I had a friend whose hedge was dying off. He thought the neighbour was poisoning it, but soil analysis didn't show anything. He then set up a surveilance camera which captured his neighbor pouring boiling water on the roots! ? Link to comment Share on other sites More sharing options...
LadyG Posted May 10, 2019 Report Share Posted May 10, 2019 2 hours ago, tree monkey said: Oy copper nails Link to comment Share on other sites More sharing options...
tree monkey Posted May 10, 2019 Report Share Posted May 10, 2019 12 minutes ago, LadyG said: copper nails Just blunts saws when the tree does need felling Link to comment Share on other sites More sharing options...
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