Metallurgy and Maple

[Barkley]

In the process of trying to understand why a stainless steel table top would become pitted I came across a book "How to Brew" by John Palmer with an excellent appendix (b) on metals used in brewing equipment and how to protect and properly maintain your investment. Also provides good information on cleaning, treating and fabricating with stainless-useful info that is adaptable for maple producers. I bought the book but it can be viewed online at http://www.howtobrew.com/ The lesson for me-stainless steel is not as indestructible as we maybe thought.

[Bucket Head]

Some cleaners (acids) will pit stainless steel. Dissimilar metals in contact with water present will corrode and pit.
Years ago I bought a stainless milker pail at an auction. It had some nails in it, so it was rusty-looking on the bottom. Took it home and scotch-brite-ed it until my fingers were sore and she looked great! Well, it leaked. Then I held the bottom up to the light and saw many, many tiny pin holes. Wherever a steel nail touched the bottom, it corroded through.

So basically I purchased an oddly shaped, stainless steel watering can.

[wiam]

I have heard horror stories about pans moved in open trucks this time of year having similar results.

[Super Sapper]

A lot will depend on the grade of stainless Type 304 is common in the dairy industry but will pit with higher levels of chlorine or hydrogen peroxide. 316 is more resistant but also more expensive. There are many other grades for other uses.

[DrTimPerkins]

We get plenty of calls from people who've done something similar with spouts. They'll toss them in a bucket at the end of the season with water and bleach. Then they go to use them the next year and find they've rusted together into a big pile of rusted metal. Strong oxidizers (chlorine and hydrogen peroxide) will do a real job on stainless pans. Acids will too if strong enough and left long enough.

[Barkley]

Interesting that a number of people have had bad experiences. What I initially blamed on a manufacturing defect or poor quality stainless steel was likely caused by leaving a steel container sitting on the stainless table top for a few months in a damp storage area.