Rust on Stainless Ring in DE Filter

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Woody007

Well-known member
Aug 20, 2020
183
Midwest US
From searching on here, seems to be a fairly common concern about the stainless ring inside the filter housing rusting.
I took mine apart and cleaned it as well as I could. Majority of the rust was from a stainless joining device where the two ends of the ring met.
Might be galvanic action, not sure.
Question is about protecting it from further rust. I decided to put some thick silicone grease on the ring and joining areas. Thought was it probably won't wash off very quickly, and I didn't want to introduce paint or some other coating.
Do you think the grease will work?
FWIW, it's a Jandy DEV 48. Contacted the vendor with no help. Said it must be my water. :(

Picture is before spending time cleaning the ring.
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I would clean the thick rust with a stainless steel wire brush and then use Bar Keepers Friend to remove the surface rust. BKF contains oxalic acid which will passivate stainless steel. I would keep the BKF away from the plastic surface.
 
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Woody007 said:
Said it must be my water.
Click to expand...
If it was your water, then the rust would be everywhere, not just one spot.

The machining by heat or stress causes changes in the molecular properties of the stainless steel and that can make it more susceptible to rust.

I would not wire brush the steel as that can cause more rust later where the steel is scratched.

Maybe make a paste of vitamin C and water and use a toothbrush to clean the rust.

A thin coating of a waterproof flexible sealant would help prevent further corrosion.

A silicone rated for Aquariums would probably work ok.


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JamesW said:
If it was your water, then the rust would be everywhere, not just one spot.

The machining by heat or stress causes changes in the molecular properties of the stainless steel and that can make it more susceptible to rust.

I would not wire brush the steel as that can cause more rust later where the steel is scratched.

Maybe make a paste of vitamin C and water and use a toothbrush to clean the rust.

A thin coating of a waterproof flexible sealant would help prevent further corrosion.

A silicone rated for Aquariums would probably work ok.


View attachment 460729
Click to expand...

I've exchanged several emails with Jandy and they totally and completely blame it on the water. Even though I pointed out it was concentrated in one area, plus my stainless ladders and light fixtures are just fine.
I sent them a spreadsheet of my water parameters and they still insist that it's the "water balance". They keep falling back to a Langlier index as their measure of balance. It appears to be a calculated parameter, which to me if all the direct measured parameters are in range that index has to be good.

It doesn't really matter to me for the one piece of SS, but it's become a point to be made now.
I feel that they use "water balance" as their way around having to cover items under warranty. I'm calling BS on that.
 
Plug your numbers into PoolMath to see where your CSI is.

PoolMath

www.troublefreepool.com www.troublefreepool.com

PoolMath

Discover the calculator behind the perfect pool, PoolMath. Dealing with pools has allowed TFP to become the original authors of the best calculator on the net.
www.troublefreepool.com
 
JamesW said:
CSI or LSI is a measure of the saturation of calcium carbonate.

So, ask them how making the water fully saturated with calcium carbonate affects the corrosion of their stainless steel.

Is their band made out of calcium carbonate?
Click to expand...
Yeah, they tried to tell me my filter was full of calcium deposits from looking at my pictures.
It's dried DE. Doh...
 
JamesW said:
Plug your numbers into PoolMath to see where your CSI is.

PoolMath

www.troublefreepool.com www.troublefreepool.com

PoolMath

Discover the calculator behind the perfect pool, PoolMath. Dealing with pools has allowed TFP to become the original authors of the best calculator on the net.
www.troublefreepool.com
Click to expand...
I came up with -0.16 using avg numbers from last season. I have no Borate information, so I left it at zero, if that matters.
 

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JamesW said:
Their filter manual does not say anything about LSI or CSI.

Their heater manual says that -0.5 to 0.5 is acceptable.

View attachment 466270

View attachment 466272



Click to expand...
Thank you for going to effort to look up those details. All I have from Jandy is the filter and I think the multi-valve (that you helped me with last summer after the nut split).
I appreciate it.
Happy Holidays!
 
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I'm no metallurgical expert, but I've always thought (perhaps too intuitively?) that something called "stainless steel" isn't supposed to rust, unless.... it's not stainless steel (or a very poor grade with too much iron in it).

Dunno... but stainless steel in a pool should NOT rust in my humble opinion.

As for the calcium saturation, anyone who uses the word 'corrosive' instead of 'aggressive' is missing the point - and a lot of people miss that point.
  • Too much acid is corrosive (e.g., to metals)
  • Too little calcium is aggressive (e.g., to pool plaster)
One corrodes the iron to iron oxide (or copper to copper oxide, etc.); the other dissolves calcium out of the plaster.
  • Different beasts.
I'm just backing up what other people correctly pointed out above - which is that unless that stainless steel ring is made out of limestone, the CSI isn't related.
 
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