(206) 949-5683, Top Rated Plumber, Seattle
Results 1 to 6 of 6

Thread: Will flux corrode copper pipe?

  1. #1
    DIY Junior Member Scott Vroom's Avatar
    Join Date
    Feb 2010
    Location
    Mountain View, CA
    Posts
    18

    Default Will flux corrode copper pipe?

    A plumber told me today that flux left on the outside of copper pipes will corrode the pipe over time. Is this true?

  2. #2
    DIY Senior Member kreemoweet's Avatar
    Join Date
    Sep 2009
    Location
    Seattle. WA
    Posts
    371

    Default

    It's absolutely true. Some fluxes are very strong, and will cause visible blue/green corrosion on copper within hours. Others may take days or weeks. When you
    see copper pipe that is all gnarley with green/blue corrosion on it, especially around the joints, it usually means some lazy plumber neglected to clean off the
    excess flux, as he is required to do by at least some plumbing codes, and certainly by the dictates of Good Practice.

  3. #3
    DIY Senior Member dlarrivee's Avatar
    Join Date
    Jun 2009
    Location
    Canada
    Posts
    1,172

    Default

    You can always tell hack plumbing by the green corrosion left behind.

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    Location
    New England
    Posts
    21,446

    Default

    Water soluable fluxes aren't necessarily as bad as the older acid based paste fluxes, but wiping the joint clean after soldering is still a good practice, regardless.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Location
    Cave Creek, Arizona
    Posts
    25,686

    Default

    I seldom "wipe" the joints, because if the soldering was done correctly the flux was evaporated by the heat. Now, however, if the plumber cools the joint by applying flux, called "expensive cooling", that flux will remain on the joint. Byt, I have seldom seen any copper really "corroded" by it.
    Licensed residential and commercial plumber

  6. #6
    Janitorial Technician nestork's Avatar
    Join Date
    Aug 2012
    Location
    Winnipeg
    Posts
    98

    Default

    I don't know about water based fluxes, but conventional soldering fluxes contain a chemical called "zinc chloride".

    At soldering temperatures zinc chloride becomes acidic and it dissolves copper oxide (the brown stuff that forms on copper) much more aggressively than it dissolves copper metal. But at room temperatures, zinc chloride is so mild that you often see soldering flux being sold in metal containers. The concern is that the acidity from the zinc chloride might do some harm over a long enough period of time.

    I'd tell you to clean it off too, but I'd also add that it's more important to clean it off of hot water piping than cold water piping, especially copper pipes used in hot water heating systems where the temperatures can be much higher.

    Conventional soldering fluxes are made from petroleum jelly (Vaseline) so you can use mineral spirits (aka: paint thinner) to clean with.
    Last edited by nestork; 10-10-2012 at 04:03 PM.

Similar Threads

  1. sweating copper pipe - flux shelf life
    By tbb2 in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 3
    Last Post: 07-30-2012, 01:48 AM
  2. how to remove plastic pipe stuck inside copper pipe
    By libinius in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 42
    Last Post: 04-01-2012, 10:16 AM
  3. Plastic Pipe Insulators / Brackets thru Studs for Copper Pipe -- When Required?
    By speede541 in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 14
    Last Post: 01-11-2011, 10:44 PM
  4. Does hand soap corrode?
    By seattleplumber in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 13
    Last Post: 02-04-2009, 05:47 PM
  5. Will Inland Salt Water Corrode Fittings?
    By Simplemountain in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 2
    Last Post: 01-24-2009, 06:59 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •