Toyota Tundra 2005 Service - Repair - Maintenance page 3507

IN-16 INTRODUCTION
PRECAUTIONS FOR REPAIRING BODY
STRUCTURE PANELS
1. HEAT REPAIR FOR BODY STRUCTURE
PANELS
Toyota prohibits the use of the heat repair method on body
structure panels when repairing a vehicle damaged in a col-
lision.
Panels that have high strength and rigidity, as well as a long
life span for the automobile body are being sought after.
At Toyota, in order to fulfill these requirement, we use high
tensile strength steel sheets and rust preventive steel
sheets on the body.
High tensile steel sheets are made with alloy additives and
a special heat treatment in order to improve the strength.
To prevent the occurrence of rust for a long period of time,
the surface of the steel is coated with a zinc alloy.
If a body structure parts are heat repaired with an acetylene
torch or other heating source, the crystalline organization of
the steel sheet will change and the strength of the steel
sheet will be reduced.
The ability of the body to resist rust is significantly lowered
as well since the rust resistant zinc coating is destroyed by
heat and the steel sheet surface is oxidized.
2. STRUCTURE PANEL KINKS
A sharp deformation angle on the panel that cannot be re-
turned to its original shape by pulling or hammering is
called a kink.
Since structure parts were designed to exhibit a 100% per-
formance when they were in their original shape, if they are
deformed in an accident, or if the deformed parts are re-
paired and reused, they become unable to exhibit the same
performance as intended in the design.
It is necessary to replace the part where the kink has oc-
curred.