Citric Acid and Rust Removal.

Re: Citric Acid and Rust Removal.

Jorge Castaneda

>Mark,

I am no chemist myself, so no help in the solution I don't know about citric acid, but to remove rust oxalic acid is very effective. Here in the hardware stores they sell it under a brand name to remove rust from sinks and bathtubs, maybe you want to look into that, it works very well.

$0.02

Jorge

Re: Citric Acid and Rust Removal.

Bryan Danner, Broad Ripple, IN

>Being a chemical engineer, my first response is to ask for more info regarding the nature of the 10% solution? Do the instructions call for molarity, molality, etc. There are lots of ways to skin a cat when it comes to acidic solutions.

Joking aside (nothing quite like chem-engineer humor, eh?), I'd probably just opt to do the mixture by weight. A 10% The solution is dilute enough that a bit of error one way or another won't really matter.

A gallon of water is a bit more than 8 lbs. So about 1 pound of citric acid to 5 quarts of water will give you something close.

-Bryan

Re: Citric Acid and Rust Removal.

Scott in Douglassville, PA

>Hey, Brian -

I'm sure you know this, and were poking fun at the spectrum of measure available in chemistry, but for those not as versed, I'll add:

• Molality is defined by moles solute per kg solvent. It's not related to percent measure.



• Similarly, molarity is defined by moles solute per liter solvent, also unrelated to percent measure.



• Unlisted above, normality is defined as equivalents solute (defined by specific reaction) per liter solvent. My experience has always used normality when dealing with acidic solution, but that may be specific to my work history.



• Weight percent is defined as percentage of solute mass per total mass of solution. For a 1000g solution of 10% wt:wt citric, measure out 100g of citric (assuming 100% citric), and dissolve in 900g water.



• Volume percent is defined as percentage of solute volume per total solution volume. For 1000mL solution of 10% vol:vol citric, measure out 100mL of citric acid, and dissolve in enough water to bring the solution up to 1000mL.

Again, I know you know this, but chemistry's a black box to lots of folks. I agree - most of these solutions are specified as weight percent.

Now, are there any waters of hydration to account for? ;)

Scott, WMU chem, MSU ChE

Smart A**...

Scott Burr in Ben Lomond CA

>Just pokin fun at you Scott.

Thanks for de-geeking that for us;)

That don't make no sense

john jesseph

>Unless you cipher in Avogadro's Number.

Re: Citric Acid and Rust Removal.

Don Thompson - Cutler Ridge, Florida

>#4 should be the right answer, I believe.

I got an answer from Ron Fenton...

Mark Harrison -- in Sydney, Australia

>You guys amaze me with the specilised knowledge you have :-) It seems that it was a harder question than I realised. Anyway, I received a far simpler explanation from Ron Fenton and he has give me permission to re-post it here:

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The exact concentration is not really important. In my original instructions I suggested a 10% w/w solution ie. 10g of citric acid dissolved in 100 g water (100 mL).

The reason that I came up with this concentration was based on an experiment that I carried out in my laboratory at the University. I took an old very rusty saw blade (with fairly uniform covering of rust) to the workshop and got them to cut it into strips (about 2 inches wide). I chemically degreased the samples and put each strip into a solution of a different concentration for about 6 hours and then visually inspected the results after cleaning them with a green scotchbrite pad. I realise that this is a relatively qualitative experiment but it gave a good indication of the results that could be expected under non-laboratory conditions.

I found that at room temperature a 10% solution (weight/weight) worked best for my samples. There was no visible damage by using a more concentrated solution. And at less than 10% there was visible rust remaining.

I am fully aware of all the Chemical methods of calculating concentrations (I used to teach this to undergraduates) but I decided to keep it as simple as possible for those with no chemical background. In reality, the solution that I use at home (and have been using the same solution for about 12 months) is just 4 litres of water with 2 handfuls of citric added a squirt of detergent and a few mLs of iso-propanol (rubbing alcohol).

Warning: While I have tried oxalic acid I found it not to be as effective and covers everything with the relatively insoluble green iron oxalate compound. Oxalic acid is very poisonous and the used solution presents disposal problems.

I hope that this information helps you and if you have any further questions please do not hesitate to contact me directly.

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Thanks everyone. I will be trying it today.