Shining Silver "Natural Armor": How Unpainted Aluminum Bodies Revolutionize Urban Transit Capacity

As the Yurikamome winds through a

forest of city skyscrapers, its silver

body catches the eye. This is more

than just a cost-saving measure; it is

the crystallization of a high-level

design philosophy aimed at lightening

the urban landscape and maximizing

transport efficiency.

For Automated Guideway Transit (AGT)

systems running on rubber tires,

weight reduction is a mission-critical

challenge to ensure transport quality.

Standard painted finishes, including

putty and paint, add approximately

100kg (220 lbs) per car—equivalent

to the weight of two passengers.

Mitsubishi Heavy Industries (MHI)

solves this with its acclaimed

unpainted aluminum body.

The process begins with Friction Stir

Welding (FSW), a sophisticated

technology that creates flat car bodies

without visible weld marks.

The surface then undergoes "hairline

finishing" (mechanical roughening) 

using high-speed rotating stainless

steel brushes, similar to an automated

car wash. Within a few days, a robust

oxide layer—a "natural armor"—forms on

the aluminum surface, protecting the

body from rust without a single drop of

paint,

This dedication to shaving 100kg

delivers immense social value.

By reducing the vehicle's weight, the

same infrastructure can carry more

people. In fact, the new Yurikamome

trainsets successfully increased their

capacity by approximately 80

passengers per train through thorough

weight reduction. This serves as a

powerful solution to urban stress, such

as overcrowding during major events.

Furthermore, lighter vehicles consume

less electricity and extend the lifespan

of components, sustaining the "urban

bloodstream" in an eco-friendly and

sustainable manner.

The subtle silver luster created by

hairline finishing does not fade for 10

or 20 years, even in harsh

environments exposed to salty sea

breezes. This silver armor, born from

Japanese "Monozukuri"

(craftsmanship), continues to protect

the comfortable daily commutes of

people on the Yurikamome, the

Nippori-Toneri Liner, and the New

Shuttle.

Stay tuned for the next AGT Blog!