How do you measure rust?

2007

A. To measure corrosion requires equipment that most middle schools do not have.
Corrosion frequently is measured in weeks, not days, so that is another problem.
You are probably stuck with visual rather than measured which is poor for a science project.
Typically, you will have your worst corrosion at the water-air interface, so you need your test panels either completely submerged or completely out of the liquid.

James Watts
- Navarre, Florida

A. Alisha,
Make up your own scale, make a series of samples that have different amounts of rust from minor to major and then record the process it went through to get to that point. Then all you have to do is assign a numerical or alphabetical value to it.

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
2007

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A. The simplest but most precise and scientific way of measuring corrosion is to accurately determine the depth of the attack. This can be done on a well designed sample that is exposed to corrosion. After a specified time, the corroded surface is removed (machined or ground) until the deepest pits or craters have been cleaned and all the metal surface is sound. With the aid of precision instruments, the initial and final dimensions are measured. The difference gives the attack depth. Other approaches are more subjective and focus on visual aspects.

Guillermo Marrufo
Monterrey, NL, Mexico
2007

A. Maybe if she could weigh and measure her samples before she starts the test and after removing all the rust with some easy mechanical method, she can get a certain idea of the corrosion rate, maybe she has to use some simple geometry of the samples (like a rod)of severals alloys in the same corrosion environment or the same alloy on several corrosion environments, just an idea, to have something to compare to.

Jessica Giacchi
- Tandil, Buenos Aires, Argentina
2007

A. To measure rust you need to take a ruler and measure it in inches.

Dustin Scott
- orlando, florida, USA
August 22, 2015

A. You need a stopwatch, a LARGE measuring cylinder, a rusty object and hydrochloric acid.

You first put some hydrochloric acid into the large measuring cylinder. You then put the rusty object in the acid. The rust will dissolve:

Fe2O3 + 6HCl -> 2FeCl3 + 3H2O

And so will the iron:

2Fe + 6HCl -> 2FeCl3 + 3H2

The reaction with the rust will produce H2O, so the volume measured in the cylinder will either increase or stay the same, and the solution will go yellow because of the FeCl3. The reaction with the "unrusted" iron will produce H2, and the measured volume will decrease. Once you get the reaction going, you use your stopwatch to measure how much time it takes for the volume to decrease a fixed amount (e.g. 100 ml). The longer it takes, the rustier the object is.

Luis Vallejo
- Auckland, New Zealand
November 12, 2019

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  Interesting idea to watch the volume drop as the acid attacks the steel and releases H2 gas. But it seems to assume that none of the other reactions cause volume changes, which may be true, but I would not necessarily assume so. Have you actually done this experiment to verify that it works? Thanks.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
November 2019

A. The simplest way to measure corrosion is weight. Weigh the sample beforehand and note the increase.

Rust may fall off iron, so have some way to account for that. You could weigh any rust that has fallen off or thoroughly dry the vessel (to remove any changes in weight from evaporation)and weigh that with the sample. Remember to put all your samples through identical procedures.

You will need very accurate scales to get meaningful data.

Ben OShea
- Katikati, New Zealand
November 13, 2019