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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Corrosion Properties of 6061-T6 in an Alkaline Environment
Q. I'd like to find out how well 6061-T6 aluminum will stand up in a mildly alkaline (limestone and water slurry) environment. Can you give me any information on what I can expect? Will I see any significant corrosion or pitting?
Thanks!
Design Engineer - St. Cloud, Minnesota, USA
2007
Aluminum will likely prove to be the wrong material for this, Phil. I don't know about pitting specifically, but I think you will get significant corrosion. Strong alkali, like caustic soda ⇦liquid caustic soda in bulk on
Amazon [affil link]
, will completely dissolve aluminum.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007
Q. I was told that the natural Oxide film was stable at pH ranges from 4-9. A typical slurry of sawn limestone dust and water has a pH of 8.0-8.4. If you think this will still be a problem, would anodizing the parts be a potential solution to any corrosion issues?
Thanks again for your help!
Phill Snartland- St. Cloud, Minnesota USA
2007
A. The anodized surface has even less resistance to alkali than raw aluminum. But I guess I don't know enough about lime and limestone. If it is pure ground limestone and there is no slaked lime included, it sounds okay.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007
A. I have my doubts as to the suitability of aluminum in contact with a limestone slurry. One, it is abrasive and and the aluminum would be eroded. If finely powdered, I suspect that the pH would slowly rise to above 9.
I would tend to lean towards stainless steel. 304 is not horribly priced compared to aluminum.
- Navarre, Florida
2007
Q. Will another alloy of aluminum, say in the 5000 series, give me better corrosion resistance, as well as mechanical properties similar to the 6061-T6? I need to keep the weight of my assembly down, that's why I'm looking at aluminum, but I need the strength of the 6061-T6 heat treated alloy. Any suggestions?
Thanks again for your help!
- St. Cloud, Minnesota, USA
2007
First of two simultaneous responses --
A. Maybe you could afford to plate your assembly? If so, electroless nickel would be my choice.
Guillermo MarrufoMonterrey, NL, Mexico
2007
Second of two simultaneous responses -- 2007
A. The biggest problem with this discussion is that you have only given us a tiny bit of the situation.
But with what you have given us so far, titanium is the best way to go. It costs more to start with, but it is lightweight and far more durable than aluminum, so will cost less in the long run and will not have the periodic shutdown for replacement that aluminum will. Anodize with a good teflon coat MIGHT work for aluminum, but it will cost fairly close to what titanium would cost. Finding the right fabricator, one that uses a lot of titanium will have expertise and lower prices for the raw material.
Now, what is the size and the use of this part?
- Navarre, Florida
Q. I have a 54" high 27' round above-ground pool. It has resin supports with aluminum walls. After the install of the pool I decided to put a perimeter around it. I came out about 32 inches and installed a level 4x4 around the entire pool. I then installed a 8-mil Visqueen about 8 inches high around the entire pool against the pool wall and secured it with duct tape. After all of that I filled the 8" high x 32" wide area with limestone gravel (57 fines).
I chose this material because it packs very tightly after being rained on a few times and my plan was to top it off with more expensive decorative washed gravel. Finally my question: Should I be concerned with the limestone gravel against the pool walls even though I installed the visqueen barrier? I am concerned about a possible chemical reaction from the limestone dust and possible slurry when it rains.
David ShanteryContractor - Montville, Ohio / United States
July 19, 2012
Hi David. Not to worry.
Even without the Visqueen I probably wouldn't be much concerned. With it, it sounds great.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 18, 2012
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