How does PLA hold in salt water ?

[Xavier Grosjean]

Hello all,

I'm rather new to 3D printing.

I'm designing and printing stuff for salt water fish tanks.

So far I've mostly used ABS, which I think is safe in salt water.

But does anybody know if PLA is okay too ? or will it corrupt quickly ?

Thanks !

[tramalot]

use polycarbonate , and soak it 24hrs and rinse it at least once, abs is safe it just gets knaury after a year or so 

[Xavier Grosjean]

Thanks !

Do you know if Wanhao Duplicator can use polycabonate filament ?

And what means "knaury" ? 

Thanks again

[Ryan Carlyle]

Nope, none of the Chinese "Replicator Clone" printers can print polycarbonate, because PC requires higher printing temps than the PTFE-lined hot ends will survive for extended periods. Also, you basically need a high-temp heated chamber or it'll warp too much to be usable. Warps way worse than ABS. 

PLA may slowly biodegrade in an aquarium environment. Various bacteria and enzymes will break it down, particularly at higher temps and in contact with water. Not sure what timeframe though -- might last a few years. It definitely lasts years in air. 

Nylon or PET should be acceptable options if you don't like ABS. PET in particular is fairly easy to print and very chemically-inert.

[Xavier Grosjean]

Thanks for all the information !

[DonaldJ]

When I read that I immediately thought "gnarly" (a word not often seen in print), which works well in this context.

On Saturday, April 25, 2015 at 2:17:01 PM UTC-5, Xavier Grosjean wrote:

[Steve Gong]

I've had PLA fish houses and other things in my freshwater aquarium for about a year now and it seems just as strong as it was when I put it in.  This is one of them

So I think if it lasts at least a year, that's good enough, and probably cheaper and easier to print than polycarbonate.  You can always just make another one if the PLA print does degrade beyond one year.  I've also been using a PLA showerhead for almost a year, and that gets subjected to somewhat high heat since I take hot showers.

One thing I have wondered is if PLA alters the pH of the water.  I guess it's acidic, but I wouldn't know if it does lower it by a substantial amount...  Any ideas?

[Xavier Grosjean]

Hi Steve, 

Thanks for the feedback and congrats for saving the cichlid :) Did they eventually get along ? I've had a couple about 9 years ago, and now I have over 30. They just can't stop.

But that's fresh water.

I'm afraid salt water can be a little worse for the PLA, all the more so with the somehow strong lights: it's a recifal tank => near-UV lights as well.

And moreover, recifal tanks are very sensitive to nitrates, so if PLA starts degrading, there could be fatal polution.

I like Ryan's suggestion to use PET, I'll try to do that.

Thanks.

[tramalot]

NOTHING like miss info to get a topic going... my lake has thawed finally . amd smell check drives them nutz... so easy

[Ryan Carlyle]

PLA should only release lactic acid at elevated temps, eg 140-150F or thereabouts. I don't think an aquarium will be an issue. 

[Matt Everest]

The alkalinity needed in saltwater/Reef tanks is very bad on PLA. It will eat it away rather quickly.

I made a couple of things for my reef tanks on the 3D printer, but I used ABS Plastic instead and have had no problems.

[Xavier Grosjean]

That's what I was afraid of...

Thanks for your advice.

For now I'm printing ABS too, and I'll try PET when I get a chance.

[mfitz73]

MadeSolid PET+ is 100% hydrophobic, from what they tell me.

On Saturday, April 25, 2015 at 2:38:20 PM UTC-4, Xavier Grosjean wrote:

[Steve Gong]

Revisiting this thread because I now have a saltwater tank.  I've tested both PLA and PETG.  Indeed it does seem like PLA degrades fairly quickly - it seems to get brittle quite fast, but I have not seen a noticeable increase in nitrates (I was experimenting with a 2cm by 4cm tube to redirect pump flow) in my 2 gallon tank.  

The PETG I'm using is eSun white.  I've printed a whole bunch of shells for my hermit crabs to change into.  PETG seems stable in saltwater and while natural is preferable, the white dye hasn't so far affected marine life.

[Enginwiz]

The white colorant in our filaments is most likely
titanium dioxide - the cheapest white pigment.
It is widely used in sun cream and provides
UV protection for printed parts in outdoor use.
White and Black are a good choice for parts
that are exposed to direct sunlight.

[Ryan Carlyle]

PLA gets brittle quite fast outside aquariums, too :-)

[tjp...@gmail.com]

Stuff I did in white PLA held up well outdoors. Stuff in black melted the first time the sun hit it.