Storage and re-drying instructions for covered electrodes
Covered electrodes are by nature hygroscopic, meaning that the cover can absorb humidity in the air. Moisture in the electrode cover can cause porosity in weldments and, for ferritic or martensitic steels in particular, the hydrogen in the moisture can also cause cracking in weldments.
In the manufacturing, covered electrodes are dried before packing in sealed plastic capsules. The plastic capsules provide firm protection against mechanical damage and protection against moisture in the atmosphere. If the electrodes are stored under normal conditions they can be stored for one year.
If covered electrodes are stored in the following normal conditions, moisture is picked up very slowly:
- 5-15°C (41-59°F): Relative humidity ≤ 60%
- 15-25°C (59-77°F): Relative humidity ≤ 50%
- > 25°C (> 77°F): Relative humidity ≤ 40%
If covered electrodes are stored in cold locations, the package should be acclimatized by reaching the surrounding temperature before the package is unwrapped.
Covered electrodes should be removed from the plastic capsules and stored in heated cabinets of 120-150°C (248-302°F) when:
- The electrodes have been re-dried
- The electrodes have been removed from the hermetically sealed capsules
At the workplace, the electrodes should be removed from the plastic capsules and kept in an electrically heated compartment of minimum 70°C (158°F).
Re-drying of covered electrodes
When covered electrodes leave the factory, the humidity level has been checked. If, however, the electrode has picked up humidity, it can easily be reconditioned. Temperature and holding time depend on the type of electrode (recommendations are given on each pack). Note that the specified time begins when the covered electrodes have reached the furnace temperature. For best drying results no more than four layers of electrodes at a time should be dried.