ALUMINUM REPAIR WORK CAUTION

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•  If aluminum alloy (hereinafter aluminum) is repaired the same way as steel sheet metal, the following problems may occur.

Safety area
Dust explosion and ignition
Quality area
Corrosion caused by cross-metal contamination
Crack
Deep scratches
Stretching
Strength degradation from excessive grinding
Poor adhesion, rust

•  Plant and workers are to abide by the following cautions to prevent these events from occurring.

Dust Explosion and Ignition

Warning
•  Because aluminum dust may explode and ignite, the following occurrence conditions must be avoided.

Event
Occurrence conditions
Dust
Explosion
Aluminum dust suspended in air (concentration of 30g/m3 or more) + oxygen + ignition source (such as welding spatter or static electricity from work clothing)
Ignition
Aluminum dust + iron oxide + ignition source (high temperatures such as welding spatter)
Aluminum dust + water

Prohibited
Use of mounted dust collector and grinder equipped with dust collector bag prohibited
Reason
To prevent explosion and ignition, caused when aluminum dust scatters and becomes suspended in the air and mixed with oxygen and an ignition source, from occurring while cleaning the dust collector filter and the dust collector bag of the grinder.
Prohibited
Cleaning aluminum dust with water prohibited
Reason
To prevent ignition caused when aluminum dust and water mix.
Implementation item
Use an explosion-resistant aluminum dust collector which can dispose aluminum dust in paper bag.
Reason
To prevent aluminum dust from scattering and becoming suspended in the air, and to avoid mixing it with water.
To prevent static electricity from occurring when dust is suctioned.
Implementation item
Temporarily store aluminum dust in a plastic bag and in a covered container so that the contents do not get wet from rain even if it is kept outdoors.
Reason
To prevent aluminum dust from getting wet when disposing it outdoors.
Implementation item
Always perform repair work after stationing a fire extinguisher for metal fires and drying sand in the work booth for aluminum.
Reason
To prevent a secondary accident caused by drainage or use of general fire extinguisher.


Corrosion Caused by Cross-Metal Contamination

Caution
•  Aluminum material may corrode if it contacts with a different type of metal. Make sure that aluminum material does not come into contact with a different type of metal by taking measures such as performing the work in a facility and with equipment exclusive for aluminum work, and using anti-corrosive surface finished parts.

Prohibited
Grinding outer aluminum panel-contact area (such as frame and hinges) with excessive force (machinery) prohibited.
Reason
To prevent surface finishing applied to outer aluminum panel-contact area for preventing corrosion caused by cross-metal contamination from being ground off.
Implementation item
Set up work booth exclusive for aluminum (slide-type curtain can be used)
Reason
To prevent steel dust entering from all sides and adhering to aluminum material.
*When using a general work booth for aluminum repair work, always clean and remove any steel dust before starting aluminum repair work.
Implementation item
Prepare machinery, protective equipment, and a tool box exclusive for aluminum, and station them in the work booth for aluminum.
Reason
To prevent steel dust from adhering to the machinery, tools, and tool box during repair work and storage.
*When using the same machinery, tools, and tool boxes for both general steel plate work and aluminum repair work, always clean and remove any steel dust before starting aluminum repair work.
Implementation item
When performing repair work, use steel tools after wrapping the contact points with tape.
Reason
To prevent steel tools from directly contacting aluminum material.
*Aluminum hammers can also be used.
Implementation item
Use polishing agents for panels and sandpaper for putty grinding work, protective gloves, and cloth for degreasing work exclusive for aluminum.
Reason
To prevent steel dust from adhering to aluminum material.
*Because it is difficult to completely remove steel dust from cloth material.
Implementation item
Use a stud pin exclusive for aluminum with a stud welder for aluminum for repairs which involve dent pulling.
Reason
To prevent corrosion of welding area caused by cross-metal contamination.
Implementation item
Use surface finished bolts exclusive for aluminum for the aluminum panel installation.
Reason
To prevent corrosion of the bolt installation area caused by cross-metal contamination.


Crack

Caution
•  Because cracking may occur, do not perform hammering or pulling work with excessive force without applying heat.

Implementation item
When hammering or using a stud welder for repair work, perform repairs while warming metal with a gas burner.
Reason
To prevent cracking when performing hammering and pulling work at low temperatures.
Implementation item
When performing repair work while warming the metal, control the temperature at around 200° C {392 °F} using a thermal crayon.
Reason
To prevent cracking caused by weakening of aluminum from excessive heating.
Implementation item
Perform a crack inspection (penetrant test) after repairing an area of extreme damage such as deformed plastic.
Reason
To avoid overlooking cracks occurring after repairing damaged area.
Possibility of cracks occurring is high even if repair work is performed while warming the deformed plastic.
Implementation item
Perform a crack inspection (penetrant test) after repairing an area of extreme damage such as deformed plastic.
Reason
To avoid overlooking cracks occurring after repairing damaged area.
Possibility of cracks occurring is high even if repair work is performed while warming the deformed plastic.


Deep Scratches

Caution
•  Because aluminum material is softer and is more susceptible to deep scratches as compared to general sheet metal, do not use tools and polishing agents for general sheet metal work and hammer and dolly which contact points are not throughly polished.

Prohibited
Use of texture hammers, flexible files, and coarse (such as #60 to #80) sandpaper prohibited.
Reason
To prevent deep scratches from occurring when the same tools as for general sheet metal work are used.
Implementation item
When using steel tools for repair work, make sure contact surface of tools are thoroughly polished.
Reason
To prevent deep scratches from occurring in aluminum material caused by scratches on contact surface of tools.
Implementation item
Use sandpaper which is finer than sandpaper used for general sheet metal work, and replace it with a new one when it becomes clogged.
(Example: For general sheet metal repair #120 and for aluminum repair #180)
Reason
To prevent deep scratches.


Stretching

Caution
•  Because aluminum material is softer compared to general sheet metal it may stretch due to grinding heat and hammering, do not continually perform grinding work and frequently use of on-dolly hammering, and excessive on-dolly hammering.

Prohibited
Continuous grinding with sander prohibited.
Reason
To prevent stretching of aluminum material due to heat generated from continuous grinding work.
Implementation item
For hammering work using a dolly, off-dolly hammering is standard. Perform on-dolly work with minimal force.
Reason
To prevent stretching caused by frequent use of on-dolly work and forceful hammering.
*Rubber hammers, wooden hammers, and plastic hammers can also be used.


Strength Degradation from Excessive Grinding

Caution
•  Because aluminum material is softer compared to general sheet metal it may weaken from excessive grinding, do not use the same polishing agents as for general sheet metal repair work.

Implementation item
Perform grind work using a sander at low speed.
Reason
To prevent weakening caused by excessive grinding at high speeds.
Implementation item
Use a non-woven fabric grinder (such as a non-woven belt) for grinding work.
Reason
To prevent weakening caused by excessive grinding with a grinding stone grinder.
Implementation item
Use a soft interface disc pad with the double action sander.
Reason
To prevent weakening due to excessive grinding by using a soft interface disc pad and reducing pressing force.


Poor Adhesion, Rust

Caution
•  Apply genuine primer to the areas where the aluminum is exposed before applying putty and surfacer. Otherwise, poor adhesion or rust may occur if putty and surfacer are directly applied to the exposed aluminum.

Implementation item
Use genuine primer on areas where aluminum is exposed.
*Always perform procedure following instruction of each paint manufacturer's instruction manual.
Reason
To prevent poor adhesion caused by directly applying putty and surfacer to the aluminum material.