Subject: Why would corroded nails with rust removed gain weight?

I rusted nails for 30 days as a science fair project.  I took them out, 
cleaned them with steel wool, and reweighed them on an electronic scale.  
I found that the weights had gone up.  This surprised me very much, 
because I thought there should have been a loss in weight because of a 
loss in the matter of the nail.  Why would this have happened?  I asked a 
chemistry teacher, and he said that it could be because of the body oils 
that got on it when I handled them, or I didn't remove all of the rust.  
Thanks.  Emily

I weighed the nails on an electronic scale that measured to the ten
thousandths before and after the experiment.  I found a weight gain from
.0312g  to  .3357g.  Do you know why this would have happened?  Thanks.
Emily

Also, I cleaned them again after I was told about the body oils, etc.  They
looked the same both times, but I had a slight weight loss when I reweighed
them after the second cleaning.  Thanks again.  Emily

I did the two experiments you asked me to do.  When I handled the nails, the
weight went down.  I tried it with two nails, twice each.  And when I
scrubbed two nails with steel wool the weights went down .0008 g and .0011
g.  How does FeOH3 become Fe2O3?  Thanks.  Emily

Another question.  How do electrolytes accelerate the corrosion process?  I
asked a chemistry teacher, but he made it sound like rusting couldn't happen
without it.  Thanks.  Emily


What is sodium silicoaluminate?  The melted snow I used had a pH of 4.5, but
when I added salt the pH was 5.3.  The salt was uniodized, but contained the
sodium silicoaluminate.  Is that a buffering agent that could have accounted
for the rise in pH, and therefore reduced the corrosiveness of the solution?
Thanks.  Emily

Response:

Re: Why would corroded nails with rust removed gain weight?
I rusted nails for 30 days as a science fair project.  I took them out, 
cleaned them with steel wool, and reweighed them on an electronic scale.  
I found that the weights had gone up.  This surprised me very much, 
because I thought there should have been a loss in weight because of a 
loss in the matter of the nail.  Why would this have happened?  I asked a 
chemistry teacher, and he said that it could be because of the body oils 
that got on it when I handled them, or I didn't remove all of the rust.  
Thanks.  Emily

I weighed the nails on an electronic scale that measured to the ten
thousandths before and after the experiment.  I found a weight gain from
.0312g  to  .3357g.  Do you know why this would have happened?  Thanks.
Emily

Also, I cleaned them again after I was told about the body oils, etc.  They
looked the same both times, but I had a slight weight loss when I reweighed
them after the second cleaning.  Thanks again.  Emily




_______________________________________________________________
I suggest an experiment:

1. Weigh a non-rusty nail and handle it for a few seconds, then weigh
   it again. Does it gain or lose weight?

2. Scrub a non-rusty nail with steel wool, then wipe it off and weigh it 
   again. Does it gain or lose weight?

	Dan Berger, Admin MadSci Network
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MadSci Network
http://www.madsci.org/
webadmin@www.madsci.org

Re: Why would corroded nails with rust removed gain weight?