The "official" listing of the electrode storage and drying
requirements, as taken from the AWS specification A5.1 ("Specification
for Carbon Steel Electrodes for Shielded Metal Arc Welding", Table A2
in the appendix). This information is extracted from this reference
but is not an exact copy since I did not want to take the extra time
to reproduce the table. I also left out some electrode types that are
not commonly used.
E6010 and E6011 (i.e. cellulosic types):
Store at ambient temperature, holding ovens are not recommended,
drying is not recommended
E6012, E6013, E7014, E7024:
Store at 60-100 deg F with maximum 50% relative humidity, holding oven
to be 20-40 deg F above ambient temperature, drying can be done at 1
hour at 275 deg F
E7016, E7018 (i.e. low hydrogen types):
Storage in ambient conditions is NOT recommended, holding oven should
be 50-250 deg F above ambient, drying can be done at 1-2 hours at
500-800 deg F.
My additional comments are as follows:
Ernie and others are correct about the E6010 (cellulosic) electrodes.
They are designed to have some moisture in the flux coating, typically
about 5%. The moisture (i.e. water) is what gives these electrodes
their deep penetration characteristic. The water molecules
disassociate in the arc producing hydrogen. The hydrogen alters the
arc physics so that the arc column constricts, thus, increasing the
energy density which produces the increased penetration. You can't
see the arc physics effects going on but you can see the increased
penetration by the arc digging into the base metal.
The E7018 low hydrogen electrodes are designed to have extremely low
moisture content (it can vary but it is typically 0.2% or less out of
the manufacturers can or out of the drying oven). The low hydrogen
characteristic is desired because of weld cracking considerations.
(Yes, this type of hydrogen delayed cracking does actually happen, but
normally on thicker material and higher strength material.) However,
for "hobby shop" welding, this type of cracking is not normally a
problem. Without proper storage (i.e. holding oven), the E7018
electrodes will still run OK, they just won't be "low hydrogen"
anymore. Eventually, the flux coating can absorb so much moisture
that it begins to degrade, but this can be a long time (months rather
than days or weeks).
Let me know if anyone has questions on other electrode types (low
alloy or stainless steel).