Electronics in Rice for Water Damage

Discussion in 'Highly Technical' started by DLeRium, Aug 1, 2012.

  1. DLeRium

    DLeRium Lifer

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    Let's say your device fell into the water. You luckily battery pulled or whatever and it hasn't died yet.

    So what now?

    Some people say put it in a bag of rice, but to me water has already seeped in.

    I understand rice absorbs a lot of water but how does it deal with water in cracks or underneath say a phone screen or somewhere where the rice isn't in contact?

    I've washed a camera before and my strategy was to remove everything and let it sit in front of a fan for a whole day. My reasoning is that *some* air will at least flow into the cracks and allow the device to dry out. Over an extended period of time like a day or two, it's pretty much dry.

    While I do understand the rice argument I see using moving air as more useful.

    Discuss.

    Edit: I suppose we can treat the rice like a desiccant, but desiccants are used to prevent moisture from building up rather than used to dry stuff. I'd like to know what's more effective.
     
    #1 DLeRium, Aug 1, 2012
    Last edited: Aug 1, 2012
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  3. DrPizza

    DrPizza Administrator Elite Member Goat Whisperer
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    Actually, I'm not so certain that air will "flow into the cracks." With the rice, it lowers the humidity.

    Hmmmm... I think I'll toss out an analogy; perhaps it will work to understand. Lets say you have the bottom of a box covered with big salt grains. You could submerge the box in a big container of water, and from one side of the container, remove almost all of the salt reaching that side of the container - keeping the water very low in dissolved salt. Or, you could put the box in a river of very salty water and have that river flow over the box, with little eddy currents forming in the box, preventing most of the salt that dissolves from rapidly being carried away by the river.

    I'm not sure if that analogy is perfect though. My preferred way is to also place the item in a very warm location. I have washed some circuit boards in the sink before, and dried them off in the oven set as low as it goes with the door propped slightly open. I discovered the hard way that the plastic case on the old Nintendos deforms at a lower than expected temperature though, and since, have been pretty hesitant to repeat that method.
     
  4. CycloWizard

    CycloWizard Lifer

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    Blowing on it will only help if the blown air is dry. The rate at which the water evaporates will be proportional to the relative humidity of the blown air. The proportionality constant will be primarily dependent on the speed at which the air is moving. If you blow humid air over it, it won't do much.
     
  5. SilthDraeth

    SilthDraeth Platinum Member

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    Opposite of the oven affect, I put things in the fridge a few days.
     
  6. Deathray2K

    Deathray2K Member

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    Putting it in a very dry environment (Such as the rice creates) is sort of like putting it in a vacuum for the moisture. Depending on how dry the air actually gets, this should work better than the fan, because it will actually draw the water out as much as possible, which the moving air might not affect at all (Especially if it's not dry itself).
     
  7. dkozloski

    dkozloski Diamond Member

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    Blow the droplets out with an air hose and finish drying with a hair dryer.
     
  8. Dude111

    Dude111 Golden Member

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    Ya I think most anything will work again IF YOU WAIT UNTIL ITS COMPLETLY DRY BEFORE APPLYING POWER! (If the voltage is TOO HIGH and you apply power when wet,it will most likely ruin it)
     
  9. Modelworks

    Modelworks Lifer

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    For electronics dropped in water, take it apart,that is the only way to be sure you will not damage it when you re-apply power. Most electronics are washed off at the factory before assembly but if some residue remained and the water blends with that and bridges some pins then damage can result. Remember the pitch of the pins in these devices are sometimes just slightly more than a hair apart, doesn't take much to bridge it and with chips running at 1.3-1.8V it doesn't take much to short something.
     
  10. HexiumVII

    HexiumVII Senior member

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    You may need to ultrasonic the innards after
     
  11. DLeRium

    DLeRium Lifer

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    Right. I live in CA so its relatively dry air that I'm talking about. I leave it by the windowsill at night and there's a good breeze.

    Back when I worked on a production floor I'd take a CDA nozzle and blow the hell out of something.

    A dry environment like rice works, but how does rice work in sucking water that's trapped within a crack or inside of the object (assuming I don't want to disassemble my point & shoot camera for example). Perhaps I need to read up more about desiccators, but from what I understand it sucks moisture out of the air, but as for water that's trapped elsewhere... shrug.
     
  12. greenhawk

    greenhawk Platinum Member

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    if it was traped in something, then how did it get in there in the first place? If there is a gap for water to enter, there is a big enough gap for moisture to get out.
     
  13. Paperdoc

    Paperdoc Golden Member

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    The key here is something called a Dynamic Equilibrium - a common concept in my field, Physical Chemistry. To keep it simpler, let's deal with the particular situation posed by OP, but in stages.

    First, assume we have a closed container (jar with lid on it) containing some dry rice grains, air, and a small mount of water molecules (vapour) in the air, as normally happens. Now the starch molecules of the rice grains have a chemical structure that is very attractive to water molecules, so some of those water molecules in the air will attach themselves to the starch rather firmly and stay there. This decreases the concentration of water molecules remaining in the air, so it's a little harder for the starch to acquire more of them. But some still do attach to the starch, AND at the same time, some that are already attached, detach and return to the air. At some point, we achieve a state of Dynamic Equilibium in which the rate of water molecules leaving the air and attaching to starch (rice grain) surfaces exactly matches the rate of the reverse - the water molecules that leave the starch surface and fly off into free air. At this point, the concentration of water molecules in the air is lower that it would be in plain room air, because the starch (rice grains) with their special affinity for water molecules has "stolen" them from the air. This is how ALL desiccants work. They don't just keep something dry - they do it by selectively absorbing water from the trapped air in a closed container, thus drying the air. (Any desiccant, including rice grains, has a limit on how much it can absorb. But for this case we are assuming that there is much more rice present that water vapour, and that limit is not a problem.)

    Now, assume that someone temporarily opens the jar and places a few droplets of liquid water on the inside of the jar, then closes the lid. We now have a new second system operating - the system of dry air surrounding liquid water droplets. Some of the water will evaporate, increasing the water molecule concentration in the air, and reducing the amount of water in liquid form. If there were nothing else operating in the jar, eventually a new Dynamic Equilibrium would be established in which the rate of evaporation of liquid water into the air is exactly equal to the rate of condensation of water molecules out of the air into a liquid form on the jar's wall. But wait! We have water-hungry rice grains sitting in the bottom! That Dynamic Equilibrium system is also working to remove water molecules from the air and tie them up on the starch surfaces. So the combined effect is to move water liquid molecules into water gaseous molecules in the air, and then to remove them from the air by attachment to the starch (rice grain) surfaces. It is an overall Dynamic Equilibrium composed of two sub-processes, and using the air in the jar as a transport medium to move the water from liquid droplets into individual molecules flying around in the air until they become attached to the rice grains. As long as there is enough dry rice to make sure there are still large numbers of starch surface sites anxious to absorb water molecules, the result will be that ALL the liquid water gets evaporated from the jar walls so they are dry, and the air in the jar is still quite dry. Thus, this system will "dry up" all the liquid water, given a bit of time for the processes to proceed.

    Third scenario: the water droplets are not placed inside the jar wall by a person. Instead, a circuit board with liquid water trapped in crevices is placed inside the closed jar. Exactly the same process occurs. Liquid water evaporates into the surrounding air through the tiny crevices and floats around in the jar as individual molecules until they get trapped on the rice grain surfaces. After a while, all the liquid water had been removed from the circuit board, and it is truly dry.

    A fan in an open space and blowing over the damp circuit board will dry things out by removing any air that contains excess evaporated water molecules and supplying fresh air. As long as that fresh air is dry, it will encourage further evaporation (drying) of liquid water from the crevices. The dryer the air, the faster you can dry out the circuit board. And of course, the faster the air flow, the faster it will dry.

    Inside a closed jar with a desiccant (like rice grains), the air is VERY dry and that speeds up the process, BUT the air flow velocity is low. If you had a container for rice and circuit board that also had space for a small circulating fan inside, that would be ideal! You would NOT want a supply of outside fresh air. All the fan is doing in this case is speeding up the flow of air (dried continuously by the rice) to enhance the process.
     
    #12 Paperdoc, Aug 31, 2012
    Last edited: Aug 31, 2012
  14. yhelothar

    yhelothar Lifer

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    Even if it dried up, the water can leave ionic particles behind.
    The safest way is to take it apart and scrub it with rubbing alcohol or electronics cleaner.
     
  15. denishowe

    denishowe Junior Member

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    Brilliant explanation.

    The last paragraph is the most interesting. Which would dry your circuit/device faster: dryer, still air (sealed rice) or moving air (almost anywhere else)? As Paperdoc says, the air transports the evaporating water away from the device, the rice just discourages it from going back again but then so would a bit of wind. I would expect moving air to dry the device faster (e.g. hair-dryers, hanging clothes out on a windy day) than the stiller, dryer air in the sealed container.

    Then there's temperature. With the same humidity, which would dry better: a warmer place with less airflow (airing cupboard, oven) or a cooler place with more airflow (outside on a cool, windy day)?
     
  16. Paperdoc

    Paperdoc Golden Member

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    As a general rule, yes, moving air is a faster way to dry something. The "if" part is; IF the air is actually quite dry - that is, low Relative Humidity. If you were doing this in your room during a four-day rainstorm outside that produced air near 100% Relative Humidity, the drying rate would be much poorer.

    Regarding your second paragraph which presents two very different scenarios, I certainly expect the cool, windy day outside with good airflow to dry better than a low-airflow warm place. The "if" part of that is in the term RELATIVE Humidity. At any temperature, air has a limit to the amount of water it can hold before it becomes saturated and starts to rain or fog up. The higher the air temperature, the higher its saturation point. That is why warm saturated air, when cooled suddenly, starts to rain. RELATIVE Humidity is the amount of water actually in the air now, as a % of the max amount of water that air could hold at that temperature. So it is possible for very warm air at higher RELATIVE Humidity to have LESS water vapor in it than cooler air at lower Relative Humidity, and it might then be better at removing water from a liquid pool. Then we get back to how much impact the air flow rate has. The several factors interact, so there is no simple rule to cover all possibilities. But this is close: moving dry air is best at removing water.

    yhelothar raised a valid point. OP's original hypothetical situation did not specify anything about the water involved. If it were pure distilled water, or nearly that clean, it would leave behind almost nothing as it is evaporated. But if it were significantly contaminated, it could leave behind a film of contaminants. The chances are that, as a really dry film, they would NOT be very conductive. Most contaminants in water that are conductive are so because they are DISSOCIATED into ions in solution. But once there is no water to be the solvent, they re-associate into non-ionized solids that are not conductive. HOWEVER, two things can happen here: (1) if any water does return, instantly there is a conductive liquid film as the contaminants re-dissolve in that new water; and, (2) the presence of the contaminants themselves MAY make it almost impossible to evaporate the last of the water, leaving a slightly conductive deposit.

    Years ago a friend had his pocket calculator drop into a large tank of a water-soluble polymer we were preparing. When we retrieved it and turned it on, the display was crazy! So we opened it up, removed the battery, and used cotton swabs, rags and distilled water to wash off everything we could, attempting to remove any contaminants. Then we left it open in the lab on the desk for several days. When re-assembled, it worked just fine!
     
    #15 Paperdoc, Feb 8, 2014
    Last edited: Feb 8, 2014
  17. Mand

    Mand Senior member

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    The mechanism here is one of vapor pressure. The more water vapor in the air, the slower any remaining liquid water will evaporate. By drying out the air, the water will evaporate more quickly. There are lots of ways to dry out air, rice just happens to be an easily accessible and cheap way of doing it.

    As far as moving air, it's the same situation. When the water evaporates, where does it go? Into the air just above the water, where it will diffuse outward. This means that the air closest to the water has the most water vapor in it, and so it will reduce the rate of further evaporation. If you use a fan to blow away the air near the water and replace it with new, dry air, then the evaporation rate will go up. If you have a large source of air you know is dry, then this is a good solution. However, it probably won't be as dry as the air would be if you were to use the rice method, by my guess.

    As far as damage due to deposited solids after evaporation, most of those won't be conductive, or if they are there probably won't be enough of it to make the sort of connections that would cause damage. I remember one particular incident that happened to the Blizzard servers running the original World of Warcraft beta when the server building got hit by a tornado. The tornado tore a big hole in the roof, and a lot of water got dumped on the servers. They waited for the servers to dry, and most of them worked afterward.
     
  18. SecurityTheatre

    SecurityTheatre Senior member

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    TLDR; The rice is more effective if the ambient air is humid, since it keeps the local air very dry. The fan would be more effective given very dry air to start with.

    P.S. Check your local humidity level (use weather.com or something). Humidity between 10% and 40% is pretty dry. Between 40% and 65% is moderate. Higher is a bit moist and probably not best.
     
  19. Z15CAM

    Z15CAM Golden Member

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    Once dry and keeping for storage "soby peripoiisi" is supposed to be good but I bought a HiFire Auto CD ignition sprayed with it and it took me days scrubbing with using alcohol and 1200 sand paper to remove it. RED RUST-CHECK is my preferred storage method whether it is electronic, guns or automotive.

    Spraying Red RUST-CHECK displaces water on Electronics then blow with Air.
     
    #18 Z15CAM, Feb 11, 2014
    Last edited: Feb 11, 2014
  20. Oyeve

    Oyeve Lifer

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    I use centrifugal force in these cases. I put my small gadget in a long towel, swing the hell out of it so the moisture goes to the outer extreme, sop up as much moisture as I can then i put in rice. Ive been 100% so far. Hell, back in 2002 we had a flood at my office and there was a thinkpad 700 under water and me and my fellow tech put in a huge beach towel and swung it for nearly an hour, put it in a big tin of rice for about a week, plugged it in and it booted right up. Even the HD was working. I did take it apart tho and rust was forming so we backed up the data and left it as a spare just in case. Well, even tho that laptop was getting rusty it still worked up until the HW was so obsolete that we recycled it.
     
  21. radtechtips

    radtechtips Senior member

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    That's interesting because there's no such thing as centrifugal force.
     
  22. sm625

    sm625 Diamond Member

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    Rice or other dessicants will help all parts dry, even the deepest cracks. The drier the air is around to the crack, the faster the water will wick out and evaporate. If you need it to dry faster, then soak the device in 99% rubbing alcohol. Then let it dry, it will dry even faster.
     
  23. serpretetsky

    serpretetsky Senior member

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    I don't understand why people say this. There's a centripetal force and a centrifugal force. They point in opposite directions as seen from different frames of reference. Why is there no such thing as centrifugal force?

    It's the same as gravity. Gravity will force an object down, but the floor will force and object up (thereby letting the object stand on a floor). Both forces exist from different frames of reference.
     
  24. Mand

    Mand Senior member

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    Because physics teachers decided there wasn't. Not physicists, teachers.

    This is because of the highly technical jargon term of "fictitious force." It exists because of the differences between rotating and non-rotating reference frames. It is only fictitious in the sense that it is not present in a non-rotating frame of reference.

    Physics teachers missed this incredibly subtle distinction, and told a generation of students that centrifugal force doesn't exist. But it certainly does, and you have to include centrifugal force if you want the equations of motion to work in rotating frames.
     
  25. mindless1

    mindless1 Diamond Member

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    Rice use is based on a myth that if something is wet then eventually getting it as dry as possible is *best*.

    There are two problems with this notion. The first is that if the device was designed to work in a normal environment, then there is no need to drop the moisture level below the ambient air level.

    Second, rather than how dry it gets, it often matters how fast it dries out. Modern consumer electronics containing solder are typically made with water soluble flux. Manufacturers rise it off but inevitably a portion remains. Sometimes so much remains that the PCB even looks like it has the equivalent of a salt film on it.

    When this flux residue gets wet it begins to leech away metal from pads and component leads. Give it enough time to leech the metal, particularly as the water slowly dries up and makes the pools of flux more concentrated in both flux strength and metal content, and you may end up with conductive shorts on the PCB which can cause malfunction or even permanent damage.

    Due to these factors it is generally best to use a two step approach if you are certain a fair amount of water has gotten into a device. Step one is to flush out the device with common 70% rubbing alcohol. The alcohol reduces surface tension and dries faster while having water helps to dissolve away and rinse out flux reside.

    The problem with this technique is some of that residue and other contaminants may get the screen or contacts dirty. It is up to the individual to decide if the risk outweighs the benefit and assess their capability of cleaning a screen or contacts where present.

    The second step is to shake then blow the rest of the water or solution away. As mentioned above it may not get the device to as low a humidity level as rice but it removes surface moisture much faster than rice, particularly if the air is heated.

    I suppose in theory you could make some kind of desiccant (rice, etc) filtered, forced air drying chamber that would remove surface moisture even faster, but if settling for one or the other mentioned methods, heated air is better when it counts.

    Lastly, consider how rice itself that has been exposed to humid air for too long is usually dried out at home... using heated air, in the oven. I'm not suggesting you bake your electronics but rice can only do so much by itself.
     
    #24 mindless1, Feb 25, 2014
    Last edited: Feb 25, 2014
  26. captainslow

    captainslow Member

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    And you know, corrosion and stuff from the water + electricity might (o_O) have a bit to do with this. The flux probably does affect the device, but the corrosion of the minerals in water will kill a device.