Mixing container: rusty screw?

[mfollen]

Hey reefers,

At the top of the inside of my mixing container are a few screws that hold the lid affixed to the container. I noticed that they appear to be discolored and may be contaminating newly mixed saltwater used in water changes.

The container is a tamco vertical natural PE tank:

40 Gallon Tamco® Vertical Natural PE Tank with 12-1/2" Plain Lid & 3/4" Fitting - 19" Dia. x 41" Hgt. | U.S. Plastic Corp.

Great for storing many industrial and agricultural chemicals, these tanks can be used indoors and outdoors. Self-supporting. A drawing is...

www.usplastic.com

Here are pictures. I’m considering unscrewing them out and cleaning the container out to remove any potential contamination.

Do you agree this is likely contaminating newly mixed water and I should remove the screws? The water never touches the top as the max I fill the container is 3/4 of the way to the top. But when mixing there is a lot of splashing which hits the screws.

Thank you very much.

 

[Ron Reefman]

That tiny bit of rust will put so little ferric oxide into your water you'd never be able to measure it. I would not worry about it at all.

 

[Jay Hemdal Verified Community Expert]

If the material is stainless, the issue is the chromium released as the material oxidizes. However, that issue is only seen in public aquariums with huge amounts of stainless in contact with the water.
stainless corrodes in anoxic environments due to what is termed crevice corrosion, so often seen on screw threads.
Jay

 

[piranhaman00]

Ive come to the conclusion over the years that rust has no negative effect on our aquariums.

 

[mfollen]

Thank you so much for the quick responses!

So the issue is likely not going to have an impact on acropora? If anything, it would be iron and chromium I would need to look for? But it likely is not of a concern and I can continue using the mixing container with these screws in place?

Thank you very much.

 

[Ron Reefman]

So the issue is likely not going to have an impact on acropora? Probably not even them.

If anything, it would be iron and chromium I would need to look for? Yes.

But it likely is not of a concern and I can continue using the mixing container with these screws in place? Yes.

Thank you very much. Happy to help.

 

[mfollen]

Great to hear. Saves me some headache this weekend

 

[WVNed]

I would replace them with some better stainless steel ones but not as an emergency. Once they rust they will be difficult to remove if you ever need to.
Not sure what the bolts hold but nylon bolts might be an option too if a lot of strength isn't required..