chemical resistance

Discussion in 'Camera Building, Repairs & Modification' started by olleorama, Feb 6, 2010.

  1. olleorama

    olleorama Member

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    How would the following materials/coatings resist the corrosiveness of photo chemicals?

    Urethane alkyd?

    Polyester?

    Epoxy resins?

    Which would be have the best resistance?
     
  2. Bob-D659

    Bob-D659 Member

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    What are you coating and what type of finish do you want? Are you looking for resistance to working solutions, or to concentrated solutions of NaOH. Epoxies are the most durable and the easiest to DIY by brush if you aren't too concerned about the look of the final finish.
     
  3. olleorama

    olleorama Member

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    Working solutions, B&W print chemistry.
     
  4. Bob-D659

    Bob-D659 Member

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    Ok, what are you coating, glass, copper, brass, 302L, 316 or 1010 steel?
     
  5. olleorama

    olleorama Member

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    Whatever will turn out to be cheapest. I may even go so low as particle board.
     
  6. David Brown

    David Brown Subscriber

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    You must be building a sink. DO NOT use particle board. or MDF. You will be sorry later.
     
  7. olleorama

    olleorama Member

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    Hmm, even if I coat the whole area (and the cuts) with polyester or epoxy? Would seem as it could be treated as being made from plastic if it were coated that way. I've seen wooden ships made from plywood coated in polyester and they seem quite fine after decades in marine environments. Although photo chemicals is probably a lot more corrosive than ocean water.

    Personal experience?

    I'm not really planning anything, just thinking in budget restricted ways. Second hand SS sinks and the likes are not really viable this time, unfortunately.
     
  8. Ian Grant

    Ian Grant Subscriber

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    Of course wood can be fully treated and made waterproof and coated, MDF should work perfectly but marine ply is possibly better. There are books and articles on how to do it.

    Personally I'd line a wooden sink with thin PVC sheet and weld or solvent cement it's seams, I made a lot of things that way in the past.

    Ian
     
  9. David Brown

    David Brown Subscriber

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    Yes. Although not with a sink, but other applications. There is plywood made for outdoor and marine purposes. Wood in boats and ships is specially treated, etc. Particle board and MDF are not and will disintegrate if it gets wet. It will fail. I am not disputing that it could probably be coated with enough plastic or other material to make it initially water proof, but if the protection gets a break in it, and the particle board does get moisture, it will swell up and begin to come apart. By the time one puts enough effort and expense into making a water proof wooden sink (or boat), it would not be much more expense to simply use a proper wood substrate in the first place. Just my opinion, of course ...
     
  10. Ian Grant

    Ian Grant Subscriber

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    David, MDF is treated unlike chip board (particle board) so has very significantly better water resistance which is major a reason for it's popularity.

    Ian
     
  11. olleorama

    olleorama Member

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    Thanks, I appreciate it. The risk you are talking about is mechanical damage to the coating, in this application (which isn't really a sink per say) that is unlikely.
     
  12. Fluidphoto

    Fluidphoto Member

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    I've had good luck with 1/2 in plywood (the cheap stuff) coated with fiberglass resin. A 24x60in sink cost me about $25. Just have to watch that you use the resin or epoxy outside as the fumes aren't too good for you.
     
  13. David Brown

    David Brown Subscriber

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    Ian:

    My "personal experience" was with MDF. It may not all be created equal. :sad:
     
  14. Bob-D659

    Bob-D659 Member

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    Exterior grade OSB is lower priced than marine grade plywood, and easily obtained. Not all MDF's are created equal. :sad:
     
  15. adyphot

    adyphot Member

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    Olleorama, the best bet is to build the sink properly with rails underneith the marine ply bottom and sides, well sealed with a waterproof glue or silicone on the sides and rails (screw them tightly to the sealant from under the rails), and take the sink to a shop to have it fiberglassed. I built my sinks and rack for my vertical washers that way, with a black gel-coat finish on the fiberglass. Make sure the gelcoat is fully cured before putting it in use. The gelcoat on mine stained a bit, but I've had no issues with mine in over 20 years or more of use. The bottom slopes to the drain, and I used plastic grids made for fluorescent fixtures, with trimmed pieces of PVC pipe glued to the bottom to level them up. They are light weight and easily removed for cleaning the sink if necessary.

    Aaron
     
  16. totalamateur

    totalamateur Member

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    My understanding is that marine grade plywood is put together with the same glue as regular plywood. The difference is that the interior sheets are higher quality, being free of knots and inclusions.

    I believe the glue in OSB is "more" waterproof than the stuff used in Plywood, but it's still fiberboard. I've used epoxy coated Grade 2 plywood for the backs of fishtanks. The main point of failure is where joined edges were not cut perfectly straight and square.


    Good luck.
     
  17. richard ide

    richard ide Member

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    Marine plywood is made with waterproof adhesive and the type I use is mahogany as well as being 3x the price. Plywood with no voids in the core laminations is commonly known as Baltic Birch. I have used some which (either Russian of Finnish) was waterproof with a thermally activated adhesive. The material I have bought in the last couple of years; I don't want to say it is for sure. As far as MDF - If I am putting expensive labour into something, I will use the best material possible.
     
  18. Rick A

    Rick A Subscriber

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    The outer surface of MDF does have some water resistance, but not much. Once you cut into it, the edges will readily accept moisture and start to swell. Even when it accepts a sealer, it will swell from the application of sealer. You can use MDO, which is commonly called "signboard" , it is for exterior applications, and made from exterior plywood faced with MDF for smoothness. If you are making a sink, use a product called "sturdifloor" it is 3/4" exterior grade plywood with a moisture resistant finish and adhesive, plus it is fairly smooth.

    Rick