©
COPYRIGHT 2000 THE ESAB GROUP, INC. LESSON
IV electrodes
are immediately packaged in hermetically sealed metal containers following the
high temperature bake.
4.3.1
Storage
and Reconditioning
- All low hydrogen electrodes will absorb some
moisture from the air after the electrode
container is opened. Therefore, those electrodes that
are not intended for use within a given
period of time must be stored in a vented oven and maintained
at a constant temperature. 4.3.1.1
Various structural and military codes
allow only specified times of exposure. These may
be anywhere from 30 minutes to 8 hours depending on the electrode alloy, the relative
humidity in the work area, and the
critical nature of the application. If the low hydrogen elec-
trodes are exposed to the atmosphere
beyond these time limits, they must be scrapped or reconditioned
by rebaking in a vented oven for a specified time at a specific temperature.
4.3.1.2 The
recommended storage and rebake temperatures for Atom Arc low hydrogen
electrodes are follows:
STORAGE
RECONDITIONED
225-300°F
1 hr. @700°F
4.3.2
Moisture
Resistant Coating
- Moisture absorption is of special concern to end-
users such as shipbuilders and oil
rig fabricators who are situated in areas of the world that
have a high level of relative humidity.
As the temperature and relative humidity increase, the
chance of absorbing moisture in the
low hydrogen coating is greatly increased. To combat this
possibility, major electrode manufacturers
have in recent years developed low hydrogen electrodes
with moisture resistant coatings. These coatings low the rate of moisture
absorp- tion in
electrodes that have been exposed to the air for extended periods, thus adding
an extra degree
of reliability to low hydrogen electrodes. 4.3.2.1
The following graphs (figure 3) give
an idea of the effectiveness of a moisture resistant
coating. The tests were conducted on Atom Arc 7018 electrodes. The
method of moisture
testing chosen by ESAB is that described in Section 25 of the AWS A5.5-96 Specifi-
cation. This method was chosen
because it satisfies the AWS specifications and is sensitive
only to water, making it one of the
most accurate and reliable methods of moisture determina-
tion currently in use.
4.3.2.2 The
AWS structural code and military specifications allow a maximum of 0.40% and
0.20% moisture content, respectively,
for E70XX low hydrogen electrodes. As shown on the
preceding graphs, the Atom Arc 7018
electrode satisfied this low moisture requirement for exposure
times beyond those normally allowed in field use.
