SS Screws safe around SW?

Reef Pilot · #1 01-09-2012, 08:57 PM

Is it safe to use stainless steel machine screws in a sump area? They won't actually be in the water, but will likely get wet from time to time.

Or do I need to get titanium or plastic screws (do they even make those)? And if so, where in Greater Vancouver (preferably Langley) could I find these?

globaldesigns · #2 01-09-2012, 09:01 PM

Quote:

Originally Posted by Reef Pilot

Is it safe to use stainless steel machine screws in a sump area? They won't actually be in the water, but will likely get wet from time to time.

Or do I need to get titanium or plastic screws (do they even make those)? And if so, where in Greater Vancouver (preferably Langley) could I find these?

I would think you would be fine. Stainless Steel doesn't rust.

I have had stainless steel clamps used in my water, without issue. So outside, I would think would be ok.

lastlight · #3 01-09-2012, 09:04 PM

I've got a pair of gear clamps on my return pump (pond pumps don't plumb nice) and the bottom one is not submerged but is most definitely rusting. I really should do something about it. I'm not sure if these are described as stainless steel or not but this might be useful to you if they are!

mark · #4 01-09-2012, 09:06 PM

depends on the type of SS

ScubaSteve · #5 01-09-2012, 09:11 PM

Resistant? Yes and no. It depends on the SS grade (18-8,304, 316, etc) but typically screws are of lower grade SS and are susceptible to attack by chloride. If they are being used in direct contact with the water they'll definitely pit. If they are just in the cabinet, they'll be fine for a while but will corrode with time, especially if they are in contact with a dissimilar metal (leading to galvanic corrosion). To be truly corrosion-resistant you'd need Bumax 88 or A286 Stainless steel. Really you should be fine if you have them, but there are better, cheaper options.

Brass, titanium, or silicon bronze are fairly corrosion resistant but are not the cheapest or easiest to find. In my opinion, the absolute best are Amour Coat alloy steel screws. They have a plastic like spray finish to them that is spec'ed to give over 1000 hours of salt spray resistance (direct spray from seawater) and are usually high grade steel (grade 8). And the best part is they are reasonably cheap. Easiest place to find any of these is through Acklands Granger in town but if you call around you'll find a lot of places have them.

What are you using them for?

Reef Pilot · #6 01-09-2012, 09:28 PM

OK, thanks for the info. I might try SS and see how they last. I just installed a new skimmer (In-280 from Boxing Day) and had to rearrange pumps and stuff in my sump, to get it to fit in properly. I had to move my DIY ATO which uses mechanical floats, and they need to be secured with screws (or something) in their new location.

tim the toolman · #7 01-09-2012, 10:52 PM

SS is a good option, as well what I did was countersink the screw and top the head off with clear silicone to prevent water from ever contacting the steel and also it peels out quite easily if you ever need to remove them.

gregzz4 · #8 01-10-2012, 12:10 AM

+1 on Nylon screws
If you can't find them easily, I've seen them in Electronic stores such as RP Electronics and MRO. Maybe you've someone out your way.

gregzz4 · #9 01-10-2012, 12:14 AM

Quote:

Originally Posted by lastlight

I've got a pair of gear clamps on my return pump (pond pumps don't plumb nice) and the bottom one is not submerged but is most definitely rusting. I really should do something about it. I'm not sure if these are described as stainless steel or not but this might be useful to you if they are!

Hey Brett,
If just your 'screws' are rusting, you may have bought HS clamps. HAS clamps have a stainless screw, not steel. You can also get nice full stainless from marine outlets that don't stretch or cut the hose.
Something like these works nice
Bad image, but the gear 'teeth' are raised, not perforated.

Reef Pilot · #10 01-10-2012, 12:35 AM

Quote:

Originally Posted by gregzz4

+1 on Nylon screws
If you can't find them easily, I've seen them in Electronic stores such as RP Electronics and MRO. Maybe you've someone out your way.

It's self tapping machine screws that I am looking for. Have never seen them in other than steel. But there is that electronics shop on 64th Ave near the Crappy Tire in Langley, so might be worth a check.

Thanks everyone for the ideas and suggestions.