Disclaimer: Long post regarding a subject that has minimum application to gas grills. You have been warned.
OK, well kinda way out in left field here. But it seems there is a good amount of knowledge about metals and their properties to include their corrosion resistance. This post applies to a septic system filter.
The guy was out to do the county mandated three year inspection/pumping today and pulling up the filter, I noticed he was being extremely carefull with it. I walked over to check it out and when he got it up, he told me they have had a lot of problems with this particular style of filter. Well six years ago, the galvanized handle on it corroded off and I had to get a long pole and afix a hook to it to snag the filter and pull it up. Yah, Duh, galvanized metal is not going to last long surrounded by sewer water. The septic was installed in 2000 so I guess almost 20 years was probably very lucky. I replaced that with a section of PVC pipe and that is still working great to this day. Well, back to today. The filter is basically a section of Plastic (probably PVC) disks spaced one on top of the other about 3/4" apart. They are (were) held together, one on top of the other with threaded steel rod. Two of the three rods were broke and before I inspected them, the guy said they were aluminum and they actually "MELT". Well, I thought, yah, no way we are talking 1000+ degrees inside a septic tank and then I though maybe he was meant to say corroded. But, as I looked at the exposed ends with the nuts on each end, I could see that they were stainless. The nuts and rod sticking out the top and bottom of the filter were in good shape and the top ones were still nice and SS shiny. I told him, it was stainless, but he continued to insist they were aluminum since they melt. On one of the broken bolts, I pulled out one half of one rod out the top and it indeed had "corroded" to the point that it broke. But, upon a close look, it does look exactly like it "MELTED". I went in and tested it with a magnet. The nut is completely non-magnetic and the rod is slightly magnetic. So, I am going to say the nut is probably 304 stainless and the rod is a 400 series stainless and just not up to 23 years of sewer water flushing over it. But, what really gets me is the fact that it does indeed look like someone took a high temp torch to it and it started to melt in places. It really does.
So, all you metalurgist wannabees and chemist wannabees, tell me the story.
I have ordered new 304 stainless rod and nuts to replace all three by the way. I figure if it lasts another 23 years, it will probably be someone else's problem at that time.
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