by Matt Joseph
Honda’s die-stamping process had
failures are usually far from obvious.
countermeasures to them. Here is
drawn the fender top metal so thin
In this case, the actual problem
one last example: In early 1977, I
that it could be moved by an under-
involved a sequence of factors and
took delivery of a new Honda Accord,
coating spray.
events that worked together to pro-
the car that arguably established
Worse, that thin metal flexed so
duce a perfect corrosion storm. Corro-
Honda as a major player in North
much during the car’s operation that
sion failure is rarely attributable to a
America. Immediately after delivery, I
Ziebart had determined that any
single cause or fault. Later Accord fend-
took the car to have it undercoated
coating applied to it would tend to
ers looked very similar to the early
by a friend who operated a Ziebart
fracture in short order. Ziebart fur-
ones, but did not suffer any unusual or
rustproofing establishment.
ther concluded that once the paint
premature corrosion problems in their
When I returned to pick it up,
fractured, it would pull in moisture
fender top areas. These problems can
my friend said, “Matt, I want to
and would quickly rust. The rust
usually be solved fairly easily, once
show you something.” He produced
would expand and release the coat-
their exact causes are known.
a memo from Ziebart’s home office
ing, leaving the thin steel bare and
The best action that you can take
in Connecticut, noting that their
wide open for corrosion.
to prevent back side-initiated corro-
franchises were required to advise
It got worse. Because the air under
sion from ruining your work is to con-
their customers that the standard
the fender tops exchanged with the
sider the possibility that it can happen,
Ziebart warranty would not apply to
air in the engine compartment, mois-
in every action that you take. Think
the front fenders of Honda Accords
ture would condense from there, as
about it when you decide on joint
sold in the United States and
that warm area cooled when the
design, or when you seal the backs of
Canada. In fact, Ziebart would pro-
engine was shut down. Cyclical
your joints. Consider it when you
vide no warranty at all on the front
engine-compartment cooling and
paint your work, or instruct someone
fenders of these cars.
condensing moisture is a natural
else on how you want it painted. In
The memo went on to state that
occurrence in many climates. This
sum, be aware of any factor, series of
the design of these fenders made it
predictably happens when an engine
factors, or combination of factors that
impossible to protect them with the
is shut down at the end of a day.
might result in a successful corrosive
Ziebart rustproofing process. As it
Ziebart was right. Its corrosion
attack on your work. Then take the
happened, my friend had another
engineers had foreseen a situation
best countermeasures that you can.
114
AUTOMOTIVE BODY WOR K AN D R UST R E PAI R
C H A P T E R 1 2
MINOR RUST REPAIR TO
A FENDER EDGE
This chapter is about a real-world
repair. Specifically, it details remov-
ing and replacing rusted metal in a
lower-edge wheel well area in the
front, right fender of a 1986 Jeep
Comanche. This type of repair is
called sectioning and is a frequent
task in the real world of autobody
metal projects.
The cause of the rust damage?
The plastic trim that covered it
trapped water, salt, and dirt, holding
them against the sheetmetal above
The first step in any rust repair job is to determine the extent of the damage.
it. As a result, the fender’s metal sur-
Picking and wire brushing are good ways to separate the sound metal from
face corroded, pitted, and rusted
the weak metal.
through in some places.
While fender replacement might
always multiple valid approaches to
But because this panel will be fitted
be an economically preferable alter-
any sheetmetal repair. The approach
with modified trim that will not
native to repairing this panel, this
taken here is one of them.
completely cover the repaired area,
demonstration project shows what
this area must have a fully finished
can be done to repair this kind of
The Approach
appearance that was not part of its
damage and how to do it. Another
original configuration. That is why
alternative, finding a used fender
Two aspects of this job are
older and more time-consuming
that is strong in this area and trans-
uncommon: Traditional metal sec-
techniques were chosen to restore it.
planting metal from it, might also be
tioning and finishing techniques are
Many people believe that these
an attractive approach. However,
applied to a fairly modern panel.
older metal-working techniques can-
finding such a fender probably
These techniques are usually res-
not successfully be applied to mod-
would be difficult. The trim configu-
erved for panels in older vehicles
ern sheetmetal because it is too thin
ration that caused this damage
because those panels are thicker and
and too hard. That is partially true.
would have caused it in identical
softer (contain less carbon) than is
Modern, thin autobody panels do
fenders in most climates. There are
the case with this 1986 Jeep fender.
not weld as easily, or file as well, as
AUTOMOTIVE BODY WOR K AN D R UST R E PAI R
115
CHAPTE R 12
Hand or power wire brushing near the
visible rust released loose paint,
Mild abrasive blasting poked holes
revealing additional weak areas
through areas where the metal was
lurking under the finish. This is
weakest. This procedure also began
Once the repair area was lightly
essential knowledge to have before
cleaning the metal in the repair area
blasted, some additional picking and
you begin repairs.
for later steps, like welding, tinning,
hand wire brushing revealed the
and filling.
apparent extent of the rust damage.
the panel steels t
hat were in use
before the 1970s. The older tech-
niques of sheetmetal work can be
applied to modern panels, but only
with great skill, time, patience, and
often with somewhat compromised
results. The approach, taken here, to
this job requires intermediate to
advanced skills.
The First Step: Evaluation
Cursory inspection of this fender
Knowing the likely extent of the
revealed that the area was suspect for
damage to this part of the fender, the
structural rust damage. Picking at it
next step was to mark it off so that a
with a scriber, and hand brushing it
repair strategy could be formulated
with a carbon-steel-bristle brush,
and followed. The marked area
indicated that the metal could be
represents the shapes and sizes of
punctured easily in this area. The
the patch parts to be fabricated.
same probing of other areas did not
go through the metal.
pect area, to ensure having sound
Light abrasive blasting of the
steel to which to weld new metal.
weak area and other suspected areas
Early in any sectioning project,
seemed to reveal the true extent of
where new metal will be fabricated to
the damage. More probing and
replace old metal, it is always advan-
This photo shows the boundaries of
brushing followed.
tageous to start an indexing system
the metal that needs to be cut out of
When the full extent of the
that will help you to accurately posi-
the panel, and replaced with new
metal to be excised in this area was
tion the new metal. In this case, sim-
metal. Note the vertical index
determined, it was marked for
ple index marks were chalked onto
markings: These were used later to
removal. It is always a good idea to
the fender, for later transfer to tem-
align the new, fabricated metal with
remove metal beyond the actual sus-
plates and to new metal.
the rest of the fender.
116
AUTOMOTIVE BODY WOR K AN D R UST R E PAI R
M I NOR R UST R E PAI R TO A F E N DE R E D G E
Removing the Bad Metal
There are many ways to remove
metal from panels. Popular among
them are: hand and power saws, nib-
blers, air or electric shears, grinding
wheels, and plasma arc cutting. Dif-
ferent methods have different advan-
tages and drawbacks in various
This saw cuts more slowly than
2
situations. The object in this kind of
the grinder, but is easier to
cutting is to do as little collateral
The first incision into the panel
control and guide accurately. It cuts
1
damage as possible, and to create as
was made with an air-driven 3-
cleanly and without any damaging heat
little distortion as is practical.
inch muffler cutter. This allowed entry
buildup, making it ideal for this job.
For this project, a very straightfor-
of the next tool, a small air-driven,
ward approach was favored. An entry-
reciprocating metal saw, used to cut
way was ground into the fender with
the diseased metal out of the panel.
an air-driven muffler-cutting wheel.
Then a small reciprocating saw blade
was inserted into the cut and moved
along the cut line. This was done
from both ends of the cut line.
Small air-driven reciprocating
saws are handy for this kind of work.
The reciprocating saw can make
The panel has the diseased
3
4
They are inexpensive, very maneu-
turns that a grinding wheel
metal removed. The excised
verable, and reasonably fast cutting.
cannot, but it causes some vibration
material was in a high-stress area of
In this case, the entire removal oper-
and shake in the panel. While one
the fender that included compound
ation took less than 10 minutes, pro-
hand is used to guide the saw along
curves and strengthening creases, to
ducing a clean separation with no
the chalked cut line, the other
deal with that stress. A good repair
physical damage to the fender
stabilizes one of the panel’s edges.
has to be structurally robust.
Planning and Modeling the Repair
With the bad metal removed, a
Good modeling is a critical step in
sketch was made of the part needed
sectioning work. It allows the metal
to replace it. We decided to make the
worker to gauge and confirm the
new part from two separate pieces
shapes and/or dimensions of new
and join them together, after each
pieces to the ones that they replace.
was tack welded into the fender. This
There are numerous ways to model
approach was selected largely because
any surface. The simplest is often the
each separate piece could be accu-
most useful. In this case, uninsulated
rately and easily fabricated on a
copper electrical wire was used to
metal edge shrinker, a tool that was
model the format of the fender’s verti-
available for this job. Fabricating a
cal edge. The more gradual curve of its
patch from a single piece of metal
horizontal (wheel arch) edge was
Planning a repair process,
1
would be more difficult, and would
transferred to a piece of insulated cop-
minutely, is one key to reducing
offer no particular structural or cos-
per wire. Forming the uninsulated
the likelihood of unpleasant surprises.
metic advantage, beyond some brag-
modeling wire to the fender’s vertical
A sketch of what the repair patch will
ging rights.
edge was easily accomplished by hand
look like is a good first step.
AUTOMOTIVE BODY WOR K AN D R UST R E PAI R
117
CHAPTE R 12
bending with a needle-nose pliers.
bends naturally into long curves. The
the sectioned area. The lateral index-
Uninsulated wire is best for accurately
latter was used to capture the gradual
ing marks on the fender were trans-
capturing small detail. Insulated wire
curve of the horizontal fender arch in
ferred to it for later use.
When bad metal is removed
The wire is shaped, checked,
A lengthwise model was made
2
3
4
from a panel, it is critical to
and reshaped, until it fits the
from another piece of 14-gauge
have some type of patte
rn or template
panel edge perfectly. Because the
electrical wire, this time with its
to record its shape and contours, so
removed metal was too deformed to
insulation on. This wire is marked with
that new metal can be formed
use as a pattern, an adjacent area
indexing from the fender that will later
accurately to replace it. This piece of
was modeled. This worked because
help to fit the panel patch accurately.
14-gauge electrical wire is easy to
the feature being modeled is
form and retains its shapes well.
consistent and continuous.
Cutting and Forming the Metal Patches
The tool chosen to perform the
This tool, a metal edge shrinker,
1
bulk of the forming work, an edge
is perfect for forming the long
shrinker, is one of the most useful
edge piece needed for this repair. As
and versatile tools in the metal
the surface between the jaws of the
worker’s arsenal. It simply and easily
tool is laterally compressed the piece
shrinks metal on the edge of a piece
curves to accommodate the shrunken
by compacting it laterally, between
area, creating exactly the kind of
two sets of jaws. In this case, a flat
curve needed for this repair part.
piece of 23-gauge body steel was cut
to rough dimensions in a shear, and
formed into roughly a right angle in
a small sheetmetal brake. At this
point, its format resembled that of a
small piece of very light angle iron.
As the metal along one edge of
the piece was compacted in the edge
which it later would be welded. After
shrinker, the body of the piece began
some fine tuning with the shrinker, a
to curve. This curvature was con-
very good fit-up was attained.
As the new edge piece was
2
stantly monitored and checked
Using the relevant index markings,
formed, it was repeatedly
against the insulated wire template,
the new piece was positioned in the
checked against the wire template
until it was very close to the tem-
fender opening and marked for
and modified accordingly. Although
plate’s shape. Then, it was indexed to
approximate cut-off length. A little
this edge shrinker has a foot control,
the marks on the fender, and checked
extra length was allowed for final fit-
using the hand lever gives the
against the fender opening into
ting, and the piece was cut with aircraft
operator better control.
