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Stainless Steel Diffuser Rusts

Egmel

Member
Joined
28 Mar 2008
Messages
729
Location
Guildford, Surrey, UK
I bought a stainless steel diffuser off ebay a couple of weeks back thinking it would be the answer to me breaking so many glass ones. It arrived and was lovely, looked good, ok quality and the replaceable ceramic discs were a plus!

I got it all installed and it produced beautiful little bubbles with no co2 escaping from the threads or anything, I was very pleased.

2 nights go by and in the morning I'm looking at an airline tube full of rusty water :( It was whipped out before the CO2 kicked in and I've not had any losses so no harm done.

I think there's a part which is either substandard stainless, or which can't cope with the acidic nature of the water/CO2 found in the diffuser. I've contacted the seller who took a while to believe me that it was rusting but who has offered me a refund.

So if you're thinking of getting one of these, they're probably great for 24/7 CO2 but I wouldn't recommend them for daylight hours people like me.

PDF with pics -> http://personal.ee.surrey.ac.uk/Personal/H.Cooper/RustingDiffuser.pdf
 
It looks like the nut has rusted rather than the diffuser itself, I'd clean it up and replace the nut with a marine grade (316) s/s one and try again.
 
OllieNZ said:
It looks like the nut has rusted rather than the diffuser itself, I'd clean it up and replace the nut with a marine grade (316) s/s one and try again.
Good call :thumbup:
Or try covering the nut with some Vaseline for a temporary measure.
hoggie
 
If you can let me have the size of the nut I can probably get a stainless one for you if I don't already have one somewhere.
 
Aqua sobriquet said:
If you can let me have the size of the nut I can probably get a stainless one for you if I don't already have one somewhere.
This may be the issue as not all stainless steels are supremely corrosion resistant. The nut may already be martensitic stainless which is easier to machine but not as corrosion resistant as austenitic(300 series) stainless. Just had another look at the PDF and it looks like the pipe may be brass which will be causing galvanic corrosion http://en.wikipedia.org/wiki/Galvanic_corrosion this can be prevented by seperating the two metals, a low strength loctite thread locker would work a treat.
 
Yes, "Stainless Steel" is quite a misleading term. Some of the stuff I have is A2 and some A4 but knowing which is which could be difficult ...!
 
Cheers for the suggestions guys, I'll have a closer look this weekend and see if I can work out which bit has actually corroded. I fear it may be the inside of the tube though, I think the problem is that in the high acidic environment caused by the CO2 the corrosion is amplified so any impurities in the manufacture will cause problems. :(
 
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