The effect of citric acid on steel
Q. I am doing a science fair project on the corrosion effect of different substances on steel. One of the substances I chose was lemon juice. (citric acid) I have to say what is in the citric acid thats causing the steel to rust. I have no idea. Can you tell me?
Thanks heaps,Emma R.
Student - Wellington, New Zealand
Citric acid reacts very quickly with iron, but does not in itself rust the iron. The water in the lemon juice will help to rust the iron, however, in the presence of air. A steel nail dropped into a citric acid solution will dissolve in a matter of hours. The same thing happens if you drop it in a bottle of "Coke", which has citric acid, phosphoric acid, carbonic acid and other things in it for flavor.
If you need help with your project, let us know. We work with citric acid products every day and have a lot of data.
Stellar Solutions, Inc.
Q. I work with pure lime, orange, lemon and grapefruit juice (which I understand contains citric acid) for a science project in school. I tested the pH value of the respective fruit juices and placed separate pieces of copper strips in each fruit juice. After a while I saw that the copper strips turned shinier than before. Is there an explanation for this?Nas Wahid
A. Pure citric acid does not corrode iron. In fact, it is a very effective rust remover and used widely for that purpose! As you have noticed, it will remove corrosion and leave clean, bare metal. Corrosion will set in due to the contact with air and humidity afterwards. I have myself cleaned rusted, chalked up cast iron cylinder heads by dumping them in citric acid solution and they came out like new.Holger Kneisner
- Braunschweig, Germany
Q. To whom it may concern,
I am doing an experiment regards on citric acid and rust in shool. As I was doing my experiment, I was curious of what is the chemical equation of the citric acid and rust or either the product of the citric acid and rust when its being reacted together. I would be appreciated if you know any of references or websites that would help me to get more information about my experiment.
Thank You.Ramona Paselio
student - Pago Pago, AS, American Samoa
Q. Hi I'm wondering for a school project will citric acid rust away a strip of copper and if so how long would it take?Jessica J.
student - Port Stephens NSW AUST
Q. In a book called 400 Hints for Homes the following sequence sequences is given for the removal of a rust stain: "Moisten with lemon juice, add salt and dry in the sun. Rinse off and repeat if necessary". Can I know the chemistry and physics of this operationMichelle
student - Batu Caves, Selangor, Malaysia
I believe all depends on concentrations. The nail in citric acid may be true at 100% concentration, but we actually demonstrate the OPPOSITE. At around 0.2% (2000ppm) of citric acid in water, a nail actually coat itself gray and ABSOLUTELY NO rust appears. Pure tap water results in comparison in ugly corrosion.
I did no detail study on concentrations and their impact.
Does anyone know at what concentrations citric acid acts corrosive, and at what concentrations it acts inhibitive on corrosion? Citric acid is actually termed to be an ANTI-OXIDANT. Go figure.
Looking for any clarifications.
- Montreal, Quebec, Canada
February 25, 2012
Q. I'm working on a project to find out why lemon juice can remove rust on a paper clip. Can anyone give me a help? I'll really appreciate that. Thanks.Ruth Yan
- Hong Kong, China
A. Hi Ruth.
Acids like citric acid dissolve metals but they dissolve rust (metal oxide) faster. Your chemistry book may tell you that an acid plus metal will yield hydrogen plus a salt of that metal.
Ted Mooney, P.E. RET
Brick, New Jersey
February 28, 2012
Q. Chinese old folks believe cooking lime juice or vinegar in a steel pot is bad for health.
So is this a myth or it is true? As there is a chemical action between citric acid and steel when heat is added, we are consuming the rust and whatever deposit in the food that are harmful of our body.
January 5, 2013
Q. What happens when you put copper, steel, aluminum, and brass in pure lemon juice? And why does it happen.Jonah [last name deleted for privacy by Editor]
- New York, New York, USA
A. Hi Jonah. Yes, that sounds like a good topic for a project. Let us know what happens when you do it, and we'll try to help you explain your results.
Ted Mooney, P.E. RET
Brick, New Jersey