Weather proof metal

Discussion in 'General Discussion' started by joie, Jan 27, 2012.

  1. joie
    joie Well-Known Member
    Hi there;

    I have a really important (for me) question for all of you.

    I want to 3d print something in antique bronze finish and leave it outside, that means bad weather, rain, sun, wind and that sort of things.

    Are shapeways metals "weather-proof"?, Can I 3d print a metal statue (for example) and leave it in my garden forever?, if not, What kind of post-process should I apply to it to be safe?.

    What do you think?.

    Thank you.
     
  2. GlenG
    GlenG New Member
    The SS print media will definitely corrode (red rust) if left out in the weather for extended periods of time. The only way to preserve the finish will be a post production coating with an industrial grade exterior clear coat designed for metals. Even this treatment will not last "forever".
    -G
     
  3. hagman
    hagman New Member
    Really? I mean it's called stainless steel after all - and tagged as dishwasher-proof = yes. Just wondereing ...
     
  4. Youknowwho4eva
    Youknowwho4eva Shapeways Employee Community Team
    Yes but it bronze infused
     
  5. stop4stuff
    stop4stuff Well-Known Member
    There are different grades of 'stainless steel', all with different degrees of corrosion resitsance. Shapeways 'stainless steel' is bronze infused 420 stainless and as you might guess from 420 the stainless is a bit of a hippie and doesn't stand up to much abuse from the elements.

     
  6. GlenG
    GlenG New Member
    Yes these comments explain the issues of corrosion resistance. Even if a highly resistant stainless alloy was used in the print medium there would still be problems on account of the bronze content. In effect, the matrix of printed/infused parts acts sort of like a battery and is subject to galvanic corrosion when wet. However, I have had large test parts out in the weather for several years now and I will say that the rust patina that has developed is actually quite aesthetically pleasing. It is also quite stabile and adherent (does not easily flake off).
    -G
     
  7. hagman
    hagman New Member
    Great to hear - experiment always beats theory :)
     
  8. joie
    joie Well-Known Member
    Hi there GlenG;

    Do you think my object can be then destroyed by weather and eventually collapse without being properly coated?, do you have a photo of your objects left outside for years?.

    Thank you.
     
  9. GlenG
    GlenG New Member
    Hi Joie,
    How long a particular object will survive before it deteriorates beyond recognition is very hard to predict. Environmental factors like air pollution or proximity to ocean salt spray and hi humidity will generally accelerate rusting. The overall design of the piece will also factor into how well it withstands the elements. Areas or details that trap standing water should be avoided. If the design is hollow then allowances for drainage (weep holes) should be made. If a piece has lots of frilly skinny bits projecting from the surface expect these features to fail before solid surface details.

    My test parts are in the form of a lifelike crab, about 6cm across, with a heavy solid body and thin legs of about 3mm dia. After 3 years outdoors the crab has an even, chocolate brown coloring. No heavy scaling and no indication of structural failure. At this rate I would expect it to be at least 25 years (probably a LOT longer) before any significant deterioration occurs. I will try to send a picture soon.

    In my opinion, if you find this natural patina acceptable, I'd say go for it. Unattended the sculpture will likely outlast you ....and your kids!
    -G
     
  10. joie
    joie Well-Known Member
    Well, I guess a little cleanning once per year may help a little... :)
     
  11. erckgillis
    erckgillis New Member
  12. GlenG
    GlenG New Member
    Public sculpture is frequently maintained with a product known as "Renaissance Wax". This is a synthetic microcrystaline paste wax of archival grade. GREAT STUFF! The finish on metal objects will definitely be extended by semi annual use of this stuff.

    I have never tried the "black oxide kit" that ERCK mentioned but even that finish would likely require some form of barrier coat to prevent corrosion. Marine grade finishes designed for metal and some types of epoxy based powder coatings do retard corrosion but when it comes to this SS print medium: RUST NEVER SLEEPS! Without periodic maintainice almost any treatment will eventually fail.
    -G

     
  13. stannum
    stannum Well-Known Member
    What was the bronze content? Being a mix, both parts should be addressed, and maybe they interact with each, making it a real special case. Wood and lead don't play nice, for example.
     
  14. Bathsheba
    Bathsheba Well-Known Member
    Another vote for rust: it's 316 stainless as it goes into the RP process, but after it's been sintered with the bronze it's definitely lost some corrosion resistance. Ferrous material on on an oxygen-water planet, what can you expect.

    If you live near the shore and there's salt in the air, that will accelerate it; I've had customers mention this.
     
  15. erckgillis
    erckgillis New Member
    Sound like we need some product testing!

    True the Brass will patina well and it's qualities are well known, Stainless for all it benefits will rust some and also on it's own is a known factor.

    The two together and any galvanic response will further effect both materials and any additional corrosives like Salt, Acid rain or other environmental factors will just also hasten the process.

    So the best bet depends on the function and esoterics of the design, a clear sealer would preserver the color but would have to be re-applied as would any wax or baked on powder coatings. Other materials would effect the color and if a natural patina is desired then more long term testing would tell us if any defects or small details would be effected by such exposures.

    YMMV
     
  16. 7777773
    7777773 New Member
    @ GlenG - I'd love to see photos of how your SS prints have held up after 3 years outdoors!
     
  17. GlenG
    GlenG New Member
    The current stainless bronze (matrix) used for SW prints is composed of approximately 60% alloy 420 stainless steel the remaining 40% is a tin bronze alloy. This is a composite of the two metals. If you look at prepared specimen under a microscope you can see the matrix like configuration of the material. In many ways this is a unique material. It has it's.............. peculiarities! What is true about the individual components is not always true of the composite. The fact is, not every aspect of its nature is known or understood as yet. Not even close to the amount of data available for commonly used metals. But the fact is, the print process works, it meets the needs for many applications and is available at reasonable cost. I would encourage any and all adventurous souls to keep experimenting and testing and then to provide feedback to these forums.
    -G
     
  18. GlenG
    GlenG New Member
    I'll send some pics and a tutorial on how to produce a controlled rust patina. The process is similar to techniques used for creating rust patinas on firearms or other decorative items. It is not difficult it just takes a bit of time (days of waiting) so it is not practical for SW to offer as an available finish.
    It might take me a week or so to get the info out to the forum.
    -G
     
  19. GlenG
    GlenG New Member
    Here is a picture of a test piece left outdoors for 3 years. After this natural weathering process, no other surface treatment has been applied to this piece. The "crab" is 2.5" across the top of the shell.
    Initially this part was lightly polished, leaving heavy print lines intact. Part was de-greased with detergent, washed in dilute acid (vinegar) and then rinsed with clean water and placed outdoors with full exposure to the elements.
    A brown/orange patina developed after about 6 months. After 1 year the coating darkened to mostly chocolate brown color and became even across the surfaces. After 3 years there is no flaking rust on the surface of this part and no indication of any structural compromise of the fine details of the legs. Crab 33.jpg
     
  20. GlenG
    GlenG New Member
    Here is another view of the same "crab" test part. The mottled coloration, varying from brown to orange is typical of natural weathering effects.

    If this part were treated to a rub down with a fine stainless steel wire brush the color would even out. A coating of oil, wax, or clear lacquer would result in an even deep brown color. I will process this part further and post the results shortly.
    -G
    crab2 33.jpg