hazard as well as an explosive. Prepare zinc chloride
under a ventilation hood, out in the open, or near open-
ings to the outside to reduce inhalation of the fumes or
the danger of explosion. It is essential that precautions
be taken to prevent flames or sparks from coming in
contact with the liberated hydrogen.
Another type of corrosive flux in use is known as
SOLDERING SALTS. Commercially prepared solder-
ing salts are normally manufactured in a powder form
that is water soluble that allows you to mix only the
After a corrosive flux has been used for soldering,
you should remove as much of the flux residue as
possible from the work. Most corrosive fluxes are water
soluble; therefore, washing the work with soap and
water and then rinsing thoroughly with clear water
usually removes the corrosive residue. To lessen dam-
age, you should ensure the work is cleaned immediately
after the soldering.
The two soldering methods most often used
are soldering with coppers or torch soldering. The
considerations that apply to these methods of soldering
are as follows:
1. Clean all surfaces of oxides, dirt, grease, and
other foreign matter.
2. Use the proper flux for the particular job. Some
work requires the use of corrosive fluxes, while other
work requires the use of noncorrosive fluxes.
Remember, the melting point of the flux must be
BELOW the melting point of the solder you are going
3. Heat the surfaces just enough to melt the solder.
Solder does not stick to unheated surfaces; however, you
should be very careful not to overheat the solder, the
soldering coppers, or the surfaces to be joined. Heating
solder above the work temperature increases the rate of
oxidation and changes the proportions of tin and lead.
4. After making a soldered joint, you should
remove as much of the corrosive flux as possible.
Sweat soldering is used when you need to make a
joint and not have the solder exposed. You can use this
process on electrical and pipe connections. To make a
sweated joint, you should clean, flux, and tin each
adjoining surface. Hold the pieces firmly together and
Figure 6-9.Soldering a seam.
heat the joint with a soldering copper or a torch until the
solder melts and joins the pieces together. Remove the
source of heat and keep the parts firmly in position until
the solder has completely hardened. Cleaning any resi-
due from the soldered area completes the job.
Seam soldering involves running a layer of solder
along the edges of a joint. Solder seam joints on the
inside whenever possible. The best method to use for
this process is soldering coppers, because they provide
better control of heat and cause less distortion.
Clean and flux the areas to be soldered. If the seam
is not already tacked, grooved, riveted, or otherwise held
together, tack the pieces so the work stays in position.
Position the piece so the seam does not rest directly on
the support. This is necessary to prevent loss of heat to
the support. After you have firmly fastened the pieces
together, solder the seam.
Heat the area by holding the copper against the
work. The metal must absorb enough heat from the
copper to melt the solder, or the solder will not adhere.
Hold the copper so one tapered side of the head is flat
against the seam, as shown in figure 6-9. When the
solder begins to flow freely into the seam, draw the
copper along the seam with a slow, steady motion. Add
as much solder as necessary without raising the copper
from the work. When the copper becomes cold, you
should use the other copper and reheat the first one.
Change coppers as often as necessary. Remember, the
best soldered seams are made without lifting the copper
from the work and
Allow the joint to
without retracing completed work.
cool and the solder to set before