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topic 38861

What are ways to measure rust?



A discussion started in 2006 & continuing through 2017

(2006)

Q. Hi, I am an 8th grade student doing a project on Nail Rusting. I have done everything on rust except that I don't know how to measure the amount of rust. I don't have a microbalance to measure the weight gain or loss and that's a problem. Is there any other alternatives to measure the amount of rust? Please help.

Ryan T.
Student - Rockville, Maryland


(2006)

A. Unless I'm misunderstanding you, how about visual? Design a visual scale that shows rust at various intervals, e.g. this nail was dipped in saltwater 3 weeks ago, this nail was dipped in salt water 2 weeks age etc, etc...if this isn't what you had in mind, a jeweler probably has a scale that would measure weight in the increments that you are looking for.
Apparently this rusty nail project is very popular with the school system.

Sheldon Taylor
Sheldon Taylor
   supply chain electronics
Wake Forest, North Carolina



Electronic scale

(2006)

!! Uncle!

I finally gave up guessing what the students were seeing and put some nails into fresh and salt water to see for myself what issues the kids are fighting against. Metal finishers might be interested or curious about it.

I had some "Grip Rite Fas'ners bright common 4d" nails that I had recently bought from Loews or Home Depot. They are labeled as made in China, and "Smooth shank, flat head, diamond point. Used for construction, carpentry and framing. Should not be used in treated lumber. Should not be used where surface rust is unacceptable." The box says nothing further about material of construction or coating except "Conforms to FFN105B and ASTM F1667 if applicable."

The nails are quite bright, shiny, and reflective. I would have guessed that they were zinc electroplated but the Grip Rite catalog says they are "Bright, uncoated steel finish intended for use where corrosion resistance is not required."

I took two pyrex dishes, filled both halfway with tap water, and added enough salt to one that the solution was saturated. Then I dropped one nail fully into each dish, and hung another nail on the lip of the dish so it was half submerged.

Rust started sooner than I expected (probably because I was still of a mindset that they were zinc plated). In less than a day there was obvious "fluffy" rust on areas of all four nails. After about four days there was no particular excess rusting at the solution level, and no rust on the non-submerged areas of the nails.

Evaporation starts becoming a significant issue even in a cool area in a waterfront house in the winter and I figured I would learn nothing about corrosion at the solution level without a more controlled test, which I didn't feel like doing, so I pushed the half submerged nails into the water.

After a week I decided to take a closer look. Both dishes had significant rust, the general look of it being like an non-coagulated waste water treatment precipitate, extremely light and fluffy, like a brown cloud in the sky, lying on/near the bottom. The dish with the saltwater had a white precipitation ring above the solution level, apparently at about the original solution level. A strange thing was that the saltwater had some flotsam in it -- a spattering of 1/8 to 1/4" diameter discs of oily stuff -- whereas the tap water had no such material.

I pulled the nails out and rubbed them down with a paper towel. Surprisingly, there was no obvious difference between the nails that were in fresh vs. salt water. Despite the rust, when rubbed down they seemed to still have no rust spots or pitting. Another strange observation was that they still had some small bright areas, bands maybe 1/16" wide. This could have been perhaps some preservative oil.

After a week I could see no conclusive difference between fresh water and salt water nails. So, students, start early because a week is not enough! I want to keep the nails in the water for a few more weeks.

Ryan, I think what a grammar-schooler might do for a rust comparison is to wipe the nails off with a coffee filter, then pour the water through the filter and see if there is a measurable visual difference in the amount of rust captured. The coffee filters can be exhibited on project night.

Good luck.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



(2006)

Q. I am an 8th grader doing a project on nail rust. I have had my nails in different liquids for several weeks. I have been recording the rusting process. My problem is that I have water from our kitchen faucet which is well water. I bought some Sea Salt, Course [linked by editor to product info at Amazon] to put in one of my containers to represent sea-water. My faucet water without the salt started to rust in less than 12 hours. It took my sea-water about 2 days to start to rust. My problem is all the research I am reading says that salt water accelerates the rusting process but, this is not true with my samples. I am thinking that because I have well water that there is something in it causing it to change what the results should be. I have now gotten tap water from my grandmothers house (which is city water to see if this makes a difference. Can you explain this to me?

Thanks,

Sherri D.
student - Fort Mill, South Carolina


(2006)

A. Okay, I'm ready to take on the school textbook authors or publishers or school science department heads about this experiment if you have gumption to chime in. I say the kids are not going to see any difference in the corrosivity of salt and fresh water in this experiment that millions of kids have been asked to do. The kids may even be encouraged to fake the answer to get the "right" answer that salt water is more corrosive. Sorry, this experiment totally fails to demonstrate that! The publishers have collected tens of millions of dollars; let's see their notes that the experiment works if conducted properly because I see no evidence at all of that :-)

If you let the nails dry, that is, if you "spritz" them daily, maybe it will work, maybe, I don't know. But if you just immerse them, there is no difference.

P.S.: I saw no difference in my nails after one week, after two weeks, or after three weeks. After 4 weeks there was very little water left in the dishes. They probably dried up in about 5 or 6 weeks and I left them dry. After being dry for a couple of weeks, I think I'm finally beginning to see some additional rusting on the salt water nails. I put water back in and will check again soon. Recognize, of course, that the salt content of the "fresh" water starts building up if you keep adding more water.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2006)

A. I reexamined the nails tonight. I emptied and cleaned out the dishes and wiped off the nails before refilling the dishes because if I added water to make good the evaporation losses the tap water would start getting too salty. I still see no difference at all between the corrosion in fresh water vs. saturated salt water after a 9-week test.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



(2006)

Q. I AM IN THE 10TH GRADE & MY EXPERIMENT IS TO SUBMERGE A NAIL, EACH IN A DIFFERENT JAR WITH WATER, ALCOHOL & VINEGAR. MY QUESTION IS WHAT IS THE BEST WAY TO MEASURE THE RUSTING OF THE NAILS IN EACH SUBSTANCE. INITIALLY I WAS GOING TO MEASURE BY EYESIGHT WEEKLY ALONG WITH TAKING PICTURES, BUT THEN I READ SOMETHING ABOUT MEASURING USING AN ANALYTICAL SCALE. IS EITHER WAY OK FOR MY EXPERIMENT. IF I NEED A SCALE WHAT TYPE IS GOOD & OF COURSE REASONABLY PRICED.

ANYTHING WOULD BE OF GREAT HELP I'M SURE.

SHELLEE KAY W.
10TH GRADE STUDENT - MIAMI LAKES, FLORIDA



(2006)

Q. It is interesting to read all the experiments submerge the nails into the water. I did not see one leaving them out of liquid. What about leaving the nails out by ocean front property and see if the saltwater in the air combined with the oxygen can promote rusting quicker than say a nail 20 miles away from the saltwater? 7th grade

Ryan P.
student - Daytona Beach, Florida



September 25, 2008

Q. Hi, I am a sixth grader and this is my first year doing a science air project on my own. My project is "What makes a nail rust more, water, regular candle wax, soy candle wax, or paint?"
My only problem right now is I have no idea whatsoever about measuring the rust! I'm thinking about visual, but I don't think that that will exactly "wow" the judges. I don't have any personal spending money, so it has to be free or of very little cost. Please, please, please, please help me!

Julia L
Student - Sebastian, Florida


October 1, 2008

A. That's the question that Ryan asked to start this thread, Julia, and that we already answered. Please help yourself by reading what is already here and, if you find it insufficient, phrasing your question in terms of what has already been said :-)

Good luck and Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



March 2, 2009

Q. Hi, I'm doing a science fair project too on rusting nails and when you measure the nails with a microbalance, they gain weight after rust was formed on them. I was wondering why? I thought that they would loose weight because rust wears away the metal but it actually gains weight soo I need to know why! Please help me! Thanks!

P.S. I'm a 6th grader and it's my first time doing science fair.

Megan J
- Lockport, Illinois


March 4, 2009

A. Hi, Megan. Rust is iron oxide. So any iron that has turned to rust will weigh the original weight of the iron that has rusted away, plus the weight of the oxygen that has combined with it to form the rust. If you could successfully collect all the rust, the rusty nail plus its rust would always weigh more than the non-rusted one, every time.

But you usually can't. The rust goes into solution and makes the water rusty, it washes away, it rubs off, etc. So depending on how much rust has rubbed off or floated off into the water, a rusty nail may weigh more or less than the original non-rusted nail.

So the real way to measure corrosion is is to weigh the nail before you start; then after the rusting period you rub off all of the rust, let it dry, and weigh how much raw metal is left. It will always be less that you started with because some of the iron was consumed as rust and you are not including that in the weigh-off.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



November 5, 2009

I need to know who to measure rust. I'm doing a project where I put several different metals in different liquids. I'm an 8th grader and I need help with my project and how to make my project better?

ben h [last name deleted for privacy by Editor]
student - indiana


November 5, 2009

Hi, Ben. You're asking a question that is already asked and answered without leaving this page :-)

Good luck!

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



November 2, 2012

Q. Hi. I am in 9th grade doing a project about rust. My question is how does the acidity affect the rate of corrosion on steel wool? I am going to measure it by soaking an inch of steel wool into vinegar, lemon juice, and 100% water. After soaking the wool in to the acids, I am going to thread the wool into a probe that has a thermometer on the top and close it by rubber stopper. Then I am going to conceal it into a test tube. What is the best way to measure rust in this case? Is it by temperature or weight

Zahraa [last name deleted for privacy by Editor]
- Irvine, California


A. Hi Zahraa. Corrosion is a chemical reaction which does release heat, but very slowly. I'm not sure whether your instrumentation will be sensitive and accurate enough to demonstrate it. I hope it is.

But you can't mix the words "corrosion" and "rust" so freely. Things can corrode without rusting. When the steel wool first starts corroding in your vinegar and lemon juice, you will see no rust because those liquids dissolve rust faster than they dissolve metal. After the acidity is consumed, I think you will see plenty of rust. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



October 24, 2017

Q. Hi. I'm looking for a way to understand a way to measure metal rust and all the websites are not giving me different metals to rust, only steel.

quintin firkus
- oak grove Minnesota usa


October 2017

A. Hi Quintin. The first thing to understand is that 'rust' has a very specific meaning. It doesn't mean corrosion, or tarnish, or dissolving, or rot. "Rust" means iron oxides, the orange-brown stuff that forms only on iron & steel, and only under certain conditions. So metals like aluminum, brass, copper, silver and zinc don't ever 'rust' because they don't contain iron, so you can't get iron oxides from them.

Although no other metals "rust", they can corrode under certain conditions.

The general way you measure corrosion is you weigh the object before your test; then, after the test, you remove any remnants of the corrosion that may be adhering to the object and you weigh the raw metal which still remains. The difference between how much metal you started with and how much metal you end up with, is the amount of metal that corroded.

But the truth is that most metals other than iron and steel corrode very little under normal circumstances, and school experiments are relatively short-term, and your access to corrosive chemicals in school is very limited ... so often times iron & steel are the only reasonable metals to experiment with. Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


November 5, 2017

A. You can easily measure amounts of "rust" in all metals. Just scratch all the rust off from the main body and measure the rust. Easy.

Andrew Wang
- Peach tree City, Georgia



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