Titanium

Features of Titanium
Building Materials

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Features of Titanium Building Materials
T003en_01_201210f© 2012 NIPPON STEEL & SUMITOMO METAL CORPORATION

Titanium, on the cutting edge of the times,
is an environmentally friendly metal.

Development of titanium building materials
Titanium building materials which have come into theworld as building materials with superior corrosion resistance to stainless steel and copper are the focus of attention among many architects because of their design properties. Nippon Steel & Sumitomo Metal has been engaged
in various technological developments necessary for
producing architectural design materials.

Titanium, an element found in 1790, wasnamed after the Titans, earth giants in ancient
Greek mythology.
Its industrial production began in around1946. Being “light,” “strong” and “rust-free,” itbegan to be applied in the aerospace, chemical, electric-power and other industries, finding
its way further into architectural, civilengineering and general-purpose applications.
Architects began to use titanium in the
1970s. Titanium’s unparalleled performance incorrosion-resistance makes many architecturaldesigns possible for structures in severely
corrosive, salty atmospheres of seashores andalso in permanent architecture (e.g., museums,
temples and shrines). Lately, titanium designs
have begun to spread to general housing also.
Overseas, in the 1990s, the use of titanium
on a massive scale by Frank O. Gehry in the
Guggenheim Museum (Spain) attracted theattention of many modern architects andspread to many countries. Demand for titanium
building materials is expected to further grow in
the future.

Notice: While every effort has been made to ensure theaccuracy of the information contained within thispublication, the use of the information is at the reader’srisk and no warranty is implied or expressed by Nippon
Steel & Sumitomo Metal Corporation with respect to theuse of the information contained herein. The information inthis publication is subject to change or modification
without notice. Please contact the Nippon Steel &Sumitomo Metal Corporation office for the latest
information.
Please refrain from unauthorized reproduction or copyingof the contents of this publication.
The names of our products and services shown in thispublication are trademarks or registered trademarks of
Nippon Steel & Sumitomo Metal Corporation , affiliatedcompanies, or third parties granting rights to Nippon Steel& Sumitomo Metal Corporation or affiliated companies.
Other product or service names shown may be
trademarks or registered trademarks of their respective
owners.

1.

Page 2〜

Basic characteristicsof titanium building
materials
Titanium offers superb properties
as a building material which isideally suited to application in ahighly corrosive environment.

Features oftitanium building
materials

2.

An extensive productmenu (Surface finish)

We continuously strive to enabletitanium to maintain its design
properties coherently, fromdesign selection, through forming
and installation, to maintenance.

We developed titanium materials
with a wide variety of surface
finishes, from those that look liketiles and are suitable for Japanese
temples and shrines, to lustrous,
colored materials that are suitable
for modern architecture.

3.
5.

A wealth ofapplication technology
Development of a material
that has little distortion
during forming(Page 14)
● Development of a suitablecleaning agent (Page 15)●

CONTENTS
Development of titanium building materials ……………………………………… 1
Basic characteristics of titanium building materials …………………………… 2
An extensive product menu (Surface finish) ……………………………………… 6
Colored titanium ……………………………………………………………………… 9
Development of titanium that does not readily become discolored ……… 10
Reduction of color-tone from one lot to another ……………………………… 13
A wealth of application technology ……………………………………………… 14
Examples of use of titanium for building applications ……………………… 16
Reference materials ………………………………………………………………… 21

Page 6〜

Page 10〜

Development of titanium that does not readily
become discolored(Note)

4.

Page 13

We developed titaniummaterials for building use that
do not easily become discoloredwith the passage of time.

Reduction ofcolor-tone fromone lot to another
With metal, the color-tone from one
lot to another poses an issue fromthe design aspect. We developed
control technology that enables alarge area to be produced withrelatively little color variation.

(Note) This product reduces the rate of discoloration with thepassage of time. It does not stop discoloration. It is notpossible to guarantee that discoloration will not occur.

11. Basic characteristics of titanium building materials
1. Unparalleled corrosion resistance

3. Light weight

Titanium, readily forming stable oxide films (in a passive
state), gives excellent performance in corrosion resistance. In
ordinary service environments of building materials, thepossibility of titanium building materials becoming corroded
is non-existent.

hot-spring resorts and the like. Titanium is a metal that
also resists such environmental pollution as acid rain.
(3) Titanium is quite free of stress, pitting, and crevice corrosion as well as other types of corrosion or problems
inherent in stainless steel.
(4) Corrosion due to contact with different metals (Refer to“Corrosion potential in sea water” on page 21)
The corrosion potential of titanium is virtually equal to thatof stainless steel, and it can be used in the same manner.
In locations where protection against contact corrosion isparamount, consideration must be given to insulation andthe prevention of condensation.

(1) Seawater corrosion resistance is comparable to that ofplatinum— suited to application in coastal areas.
(2) Excellent corrosion resistance to corrosive gases(sulfurous acid gas, hydrogen sulfide gas, etc.)— suited to application in large cities, industrial areas,
Table 1. Comparison of weather resistance
between various metals

Table 2. Comparison of chemical resistance between various metals(Source: Japan Titanium Society)(Source: Japan Titanium Society)

Titanium Stainless steel Copper
SUS 304
Sea salt particle
resistance (pitting)Ultraviolet ray
resistanceAcid rain
resistance (pitting)Titanium

Stainless steel
SUS 304

Stainless steel
SUS 316

Copper

Sea water

◎

◎＊

◎＊

○

◎

△

○

◎

◎

◎

Hydrochloric acid

○

×

×

×

◎

△

△

Sulfuric acid

○

○

○

○

Nitric acid

◎

◎

◎

×

Caustic soda

◎

◎

◎

◎

Sodium chloride

◎

○

○

◎

Chlorine gas

◎

×

×

×

Hydrogen sulfide gas

◎

○

◎

×

Sulfurous acid gas

◎

○

○

×

Room temperatureHCℓ 10%; Room temperature

H2SO4 10%; Room temperature

Acid rain
atmosphericresistance◎△Contact corrosion
resistance＊◎

×Corrosion fluidity
resistance

◎

○

×

Thermal resistance

◎

◎

◎

Erosion resistance

◎

◎

○

×

HNO3 10%; Room temperature
NaOH 50%; Room temperature△

NaCℓ 20%; Room temperature
Cℓ2 100%; Wet

H2S 100%; Wet

Rating: ◎Excellent ○Good △Fair ×Poor
corrosion: The phenomenon in which a metal itself
corrodes due to contact with extraneous matters＊Contact

SO2; 30–90C

The specific gravity of titanium is 4.51– 60% that of steel, half that of copper and 1.7
times that of aluminum. Being such a lightweight metal, titanium imposes less burden
on a structure, and permits ease of fabrication.
According to use, it eliminates the need for corrosion-combating expenses, andenables further weight reduction.

4. Minimum thermal expansion
Titanium’s coefficient of thermal expansion is half that of stainless steel and copperand one third of aluminum. Having a thermal-expansion coefficient quite near those ofglass and concrete, titanium can be used in combination with these materials.
Thus, with little susceptibility to expansion or contraction from temperature changes,
titanium offers great ease and freedom in design and execution in long-term use.

5. Excellent aesthetic qualities
Titanium itself has an excellent texture and has a tastefully subdued silver color.
Titanium is also available in many varied colors developed by the anodic oxidation
method.

6. Environmentally soundTitanium is an innoxiously metal.
Only slight dissolution of metal ions makes titanium a very friendly metal to humans
and the environment.

7. Others
Among the other major properties titanium offers are:
① Small Young’s modulus (elastic modulus).
② Small thermal conductivity.
③ A high melting point.
④ Non-magnetism.

Rating: ◎＜0.05 ○0.05〜0.5 △0.55〜1.27 ×＞1.27 mm/year＊Pitting and crevice corrosion are likely to occur.

Table 4. Comparison of physical properties between titanium and other metals

2. Great strength
Titanium is almost as strong as steel, and it is the strongest of all metals for its mass or
the strongest in terms of specific gravity. For application as a building material, JIS Type
1 — which is highly workable — is mainly used.

Item
Melting point

Chemical composition
H

O

N

Fe

C

Ti

JIS Type 1 ≦0.013

≦0.15

≦0.03

≦0.20

≦0.08

Remainder

270 – 410

≧165

≧27

180°

Thickness by 2

JIS Type 2 ≦0.013

≦0.20

≦0.03

≦0.25

≦0.08

Remainder

340 – 510

≧215

≧23

180°

Thickness by 2

≦0.013

≦0.30

≦0.05

≦0.30

≦0.08

Remainder

480 – 620

≧345

≧18

180°

Thickness by 3

JIS Type 3

2

4.51

7.93

8.4
0.041

°C

Specific gravity
Thermal expansion coefficient
Thermal conductivity

Bend test
Mechanical properties(thickness: 0.5-15 mm, excl.)(thickness: 0.5-5 mm, excl.)
Tensile strength Proof stress Elongation Bend
Inside radius(N/mm2)(N/mm2)(%)
angle

Stainless steel
SUS 316
1,370〜1,397

Titanium×10-6/°C (20〜100)

Table 3. Specifications for pure titanium for industrial use (JIS products)

1,668

Stainless steel
SUS 304
1,398〜1,453

Metallic materials

caℓ/cm2/sec/°C/cm

Iron

CopperAluminum

1,530

1,083

660

8.0

7.9

8.9

2.7

17.3

16.0

12.0

17.0

23.0

0.039

0.039

0.150

0.920

0.490

Electric resistance

μΩ-cm

47

72

74

9.7

1.7

2.7

Young’s modulus

Kg/mm2

10,85019,30019,30021,00011,000

7,050

Titanium is officially approved as a non-combustible material.
(Minister of Land, Infrastructure and Transport Certification No. “NM-8596”)31. Basic characteristics of titanium building materials
8. Survey data on corrosion resistance

9. Workability(1) Data on corrosion tests of metallic materials in spa areas
Corrosion of metallic materials at spa areas is a frequent cause of a variety of environmental problems and accordingly it is necessary to pay prudent attention in selecting
metallic material for service in these areas. As a typical example of corrosion tests
conducted at spa areas, the test results obtained at the Zao spa, an area noted for its
high acidity, are introduced below.
(Source: Titanium and Zirconium , Vol. 35, No. 4 page 22, October 1987)(1) Formability
There are no particular differences between titanium andordinary and stainless steels. In the case of titanium JIS Type1, it can be formed employing practically the same tools, jigs,
etc., used for ordinary and stainless steels.
Due attention should be paid to the larger spring-back oftitanium than ordinary and stainless steels.

are applied, stricter welding control than for stainless steel
such as the necessity of argon gas shielding is required fortitanium. There are no fears of weldment corrosion andstress-corrosion cracking.
Nippon Steel & Sumitomo Metal holds titanium welding
training courses periodically to provide appropriate guidanceon welding technology.

Table 5. Major constituents of the Zao springwater(2) Weldability
Seam and spot welding can be applied to titanium under thesame atmospheric conditions and manner as for stainlesssteel. When general welding methods (mainly TIG welding)(3) Bonding and adhesion performances
Titanium’s bonding with visco-elastic and sealing materials
and adhesion to coating film are identical to those of stainless steel and aluminum.

Temperature (°C)

pH

Cℓ-

SO4 2-

Fe2++Fe3+

Springhead

52.5

1.30

738.6

5,070

94.3

Public Bath

46.7

1.35

845.3

5,460

106.0

Due attention should be paid as corrosion conditions differ according to the composition of springwater.

Pure titanium
Stainless steel SUS 304＊

Immersion at
the springhead0

Exposure at an interiorwall of the bathhouse0

Exposure at an exteriorwall of the bathhouse0

Immersionin the bath
0—Melted＊1.99—

Melted＊＊Melted

41.55

19.33

Melted＊Ordinary steel product SS400

46.22

Tough-pitch coated steel

73.66

165.94

64.83

17.11

31.77

Pure zinc metal

0.66

Melted＊＊

2.39

0.55

Melted＊＊Aluminum 5052

0

74.77

0

—

109.49Nickel0.66

341.44

3.83

1.83

58.49

Melted within two months＊＊ Melted after immersion of 10 days, —: abnormal value

dripping of acid raindrops. Further, the copper has a possibility of being corroded by decoction from mortar andfumigated tiles. Such corrosion and other problems affecting
copper application have become a notable issue from theviewpoint of the protection of cultural assets and thus expectations are becoming high for titanium application.
(Application examples: priests’ living quarters at Ikkyuji
Temple, tea-ceremony houses at Koetsuji Temple, Naritaya
and Yakuoin Temples, others)
Photo 1 shows the results of simulated raindrop corrosion tests by dripping synthetic acid rain [H2SO4 : HNO3 : HCℓ=1.4:1.4 (mol ratio), pH=4.6].

Photo 1. Metallic surfaces after simulated raindrop corrosion tests by dripping synthetic acid rain
Ti (alumina blast finish)After
2 daysAfter
66 daysCu
After
2 daysAfter
66 days

Most of the execution methods for exterior materials (roofing and walling) of conventional metals can likewise be applied to titanium.

(unit: mg/dm 2/day)Exposure at the
springhead
0(2) Results of surveys on acid rain by Nippon Steel &Sumitomo Metal(Research into application of titanium for the protectionof cultural assets)
Copper has been applied as the material for roofing ofshrines and Buddhist temples because the copper surface
develops deep verdigris. However, deterioration of theenvironment such as acid rains is causing diverse problems.
The adverse effect of acid rain on copper application lies inthat unstable basic copper sulfate is formed rather thanstable basic copper carbonate (verdigris). This phenomenon
poses not only aesthetic but also corrosion problems, inparticular pitting corrosion (raindrop corrosion) caused by the

10. Execution and applications
11. Economics
Titanium, when used as a roofing andexterior material, may seem rather
expensive in initial coat on a basemetal basis in comparison with othermaterials. But, the elimination of
re-painting, re-roofing and other suchneeds brings running costs steeply
down to an extremely low level. Overa long span of 20 to 30 or more
years, titanium will come out a winner
in terms of life-cycle cost.
This advantage becomes evenmore marked in highly corrosive
environments such as coastal, industrial and urban areas.

An example of construction cost comparison
between titanium and prepainted stainless steel

Maintenancecost

Fabrication+
Execution

Maintenance
cost
Maintenancecost

Material

TitaniumAt the time of completion

Fist repair

Second repair

Third repair

Fluorocarbon resin paint-coated stainless steel[Conditions] Construction method: Welding method
Application conditions: Titanium — Basic texture
Stainless steel — Fluorocarbon resin paint-baked
Repairing cycle for stainless steel: 15 to 20 years before first repair, and thereafter repainting /repair every 5 to 10 years.

Range of availability of our products (Cold rolled sheets)
Coils

Sheets2.0

2.0

Thickness (mm)Table 6. Degree of corrosion of various metallic materials obtained in the corrosion test at the Zao spa(Exposure period: 6 months)

Roll dull, Pickling dull

Thickness (mm)(unit: mg/kg)

1.5
1.2
1.0

Alumina Colored
blasting titanium

0.4
0.3

70

350

650

Width (mm)* Colored titanium: Max. 2,400 mm in length

Roll dull, Pickling dull, Alumina blasting dull

1.5

Colored titanium
0.4

1,000

1,219

0.3

300

1,100

1,219

Width (mm)*Please feel free to contract us to discuss manufacturing to order outside of the values and specifications stated above.

45

2–1. An extensive product menu (Surface finish)[Pat. No. 3688762, No. 3406726, No. 3397927,
No. 3117876, No. 3453257, and No. 3655932]

Nippon Steel & Sumitomo Metal has an extensive menu of titanium materials consisting of various
combinations of three kinds of surface finish and several tens of colors which are suitable for applications ranging from modern buildings to traditional Japanese buildings and also monuments.

A

B Alumina blasting finish

Alumina powder is blasted directly
onto the titanium.

●2003 Good Design Award“Titanium temple roof/
Titanium project for protecting historical buildings”● Fiscal 2005 Otani Art Museum Award

Roll dull finish (ND10, ND20, SD3)

“A roof made of dream material that has traditional beauty
Alumina blasting finish titanium roofing and exterior materials”+ Coloring (anodic oxidation)＊

B Alumina blasting finish (AD03, AD06, AD09)
C

Pickling dull finish＊ (VP20)

A Roll dull finish

Alumina blasted titanium, which is aimed at creating the appearance of smokedtiles, is used on traditional Japanese buildings, particularly temples and shrines.

Showa Hall＊

See Page 8.

Koetsuji Temple/Main hall＊

Please contact us if you would like to request acid pickling with a dull finish.

Surface: Alumina blasting(AD09)
Area: 4,200 m2
Weight: 56 tons
Completed: 1998

Surface: Alumina blasting(AD03)
Area: 700 m2
Weight: 1.2 tons
Completed: 1997

Roll dull, which is our main product, is used on a great many buildings.

After vacuum annealing (VAF), titaniummaterials are dull-finished on a skin-pass mill.

Daichuji Temple
Surface: Alumina blasting(AD03)
Area: 660 m2
Weight: 1.2 tons
Completed: 2006

Spherical observation deck at Fuji Television’s headquarters

Hefei Lakeside International & Convention Center

Surface: Roll dull (ND10)
Area: 2,800 m2
Weight: 14 tons
Completed: 1996

Surface: Roll Dull (ND20)
Area: 13,000m2
Weight: 21 tons
Completed: 2011

C Pickling dull finish

A dull-finish is given by pickling andskin passing.

Saemangeum
Exhibition Center
Surface– Roll Dull (ND20)
Surface: Roll Dull
(ND20)
Area: 4,300m2
Weight: 10.4 tons
Completed: 2011

6

When titanium is pickled, it appears whitish. This is a representative example whichshows that color-tone from one lot to another over a large area can be reduced.

Shimane Art Museum
Surface: Pickling dull
(VP20)
Area: 10,000 m2
Weight: 60 tons
Completed: 19987

2–2. An extensive product menu (Surface finish)
A Roll dull + color finish

Colored titanium
Coloring of titanium
We have constructed a quality control setup that enables
us to stably provide colored titanium construction material.
① Uniform color② Technology for ensuring adhesion of the film
③ Development of new products④ Development of color forming protective film, and so on

Principle of coloring of titanium
Surface: Roll dull (ND20), green coloring
Area: 1,700 m2
Weight: 6 tons
Completed: 1998

B Alumina blasting + color finish

Coloring (Anodic oxidation)
When a thin oxide film (colorless and transparent) isformed on the titanium surface by means of the anodic
oxidation method, color can be seen as a result ofinterference of light. A wide range of colors can beproduced by changing the film thickness.
Principle of interference color

Oxide film
Titanium

Relationship between film thickness and interference color(Theoretically calculated values)
Green
PurpleYellow＊2
Color tone

Uchinada Town Office

Olive
green
Blue
PurpleYellow＊1
Gray0

Kitano Tenmangu/Treasury

Nara National Museum (No. 2 Annex)

Surface: Alumina blasting (AD09), verdigris coloring
Area: 1,000 m2
Weight: 4 tons
Completed: 1998

Surface: Alumina blasting (AD03), brown coloring
Area: 6,000 m2
Weight: 12 tons
Completed: 1998

When using colored titanium, please understand the following points.
① The oxide film on the surface of titanium is extremely thin, so thecolor tone is strongly influenced by the surface conditions of thebase metal.
Titanium sheets that have different surface finishes may appear
different in color, even if the titanium oxide film formed on them is thesame thickness. Also, even if sheets have the same surface finish, thecolor will differ slightly from one coil to the other.
For this reason, in addition to checking the color using color
samples, we check the color of the actual ordered material by coloringa part of the material prior to the actual coloring process. When you
intend to use two or more coils, we recommend that you control thecoils jointly with the fabricator so as to minimize color differences.
② Because titanium is colored by light interference, the color may
sometimes appear different depending upon the season, weather,time of day, and viewing angle.
When it rains, for example, the same color can look completely
different. This is a feature of interference colors, and you may find thatsuch a color change is a pleasing aspect of colored titanium.
③ The oxide film may grow depending upon the weather
atmospheric conditions, causing the color to change.

8

Ashitaka Shrine

Ryukotokuji Temple

Surface: Alumina blasting (AD09), verdigris coloring
Area: 440 m2
Weight: 0.4 tons
Completed: 2006

Surface: Alumina Blasting (AD09), Verdigris coloring
Area: 2,500m2
Weight: 5.9 tons
Completed: 2009

0.05

0.1

Film thickness (μm)

0.15With our titanium products, there have been cases in which theoxide film grew, causing the color to change from yellow (＊1) whose
film thickness is thin, to purple over a period of about 10 years. The
main factors contributing to this phenomenon are the extreme thinness
and the narrow range of the oxide film required to produce the initial
yellow color.
For a customer who wants yellow, we recommend yellow (＊2)
because the oxide film needed to develop the color is relatively thicker
and the oxide film range of that color is comparatively less narrow.
Customers should note, however, that the color of any coloredtitanium may change gradually with time depending upon the environmental conditions.
＊The hue changes in the sequence gray, yellow, purple, blue, olive green, yellow, purple, and green,as the thickness of the oxide film increases.

④ Titanium becomes dirty like other metals. Finger marks get on it.
Depending upon the type of contamination, the titanium surface
may appear discolored, but the contamination can be removed withdetergent. Note, however, that if the contamination is allowed toremain, it may become difficult to remove.
We recommend that you use a neutral detergent or ourrecommended detergent to clean titanium. If you use a detergent
that contains a strong acid, the oxide film on the surface may dissolve,
preventing the original color from being restored. (See Page 15.)9

3–1. Development of titanium that does not readily become discolored[Fiscal 2004 Japan Institute of Metals Technical Development Award; Pat. No. 3566930, and No. 3406898]

We developed titanium for building use that does not readily become discolored, and at present
we use it for all building material products (surface finishes) including colored materials.
As a result of exposing titanium for four years in Okinawa, only a very small amount of discoloration
occurred in titanium for building use that does not readily become discolored.

When titanium for building use that does not readily become discolored is colored, the discoloration resistance improves remarkably.

Exposure test for titanium building material that does not readily become discolored

Application to coloring of titanium for building use that does not readily become discolored● The pH value of acid rain in Okinawa is roughly the mean value (pH 4.8, in 2003), but because of the high temperature● The graph below shows the results of exposure of titanium of the color corresponding to a thin film at which theand humidity this is one of the regions in the Japan where discoloration occurs most rapidly.
● The mean pH value of acid rain throughout Japan is pH 4.7, (2003 data). Note: pH 5.6 or less is acid rain; Neutral is 7.0.

discoloration occurs most easily (gold or yellow), in Okinawa. Even after three years’ exposure, the change in color
difference of the material, which does not readily become discolored, is very small.
● The Zamami Pier (made of material that does not readily become discolored) retains its gold color two and a halfyears after it was constructed in Okinawa.

35

Untreatedconventional
material(Much TiC)

: Untreated conventional material(vacuum-annealed): Conventional pickled material: Material that does not readily
become discolored(vacuum-annealed)30
25

Color difference

Material that
does notreadily become
discolored(Reduced TiC)

Results of 4-year exposure test in Okinawa

Zamami Pier, Okinawa Prefecture

20

12

15

10

10

8

5
※Colordifference: 2〜3※Color difference0: 30 or more

5

10

15

6
4
2

Accelerated test of titanium building material that does not readily become discolored
Results of accelerated test
(The top 1/5th is the color prior to the accelerated test.)
Material that
does not readily
becomediscolored(pickled)

0

1

2

3

Exposure period (years)
Completed 2002 (Photographed 2004) [Thin film gold color is maintained(Material which does not readily become discolored)]Note: In the above color difference range, the color difference and oxide film
thickness are proportional to each other, so the growth of the oxide
film on the treated material is not linear.

Results of discoloration accelerated test of vacuumannealed and pickled titanium (pH 4 sulfuric acid, 60°C)
35

Material that
does not readily
becomediscolored(vacuumannealed)30
25

Color difference

Conventional
pickledmaterial

pH4, sulfuric acid

: Untreated conventional material (vacuum-annealed): Conventional pickled material: Material that does not readily become discolored(pickled): Material that does not readily become discolored(vacuum-annealed)

20
15
10
5

0

5

10

Test period (days)

10: Gold colored untreated titanium material: Gold colored titanium material that
does not readily become discolored

Test period (years)

We established an accelerated test method that reproduced the discoloration.
As a result of this test, it was found that titanium for building use that does not readily become discolored undergoes relatively little discoloration compared to untreated material.

Untreatedconventional
material(Vacuum-annealed)Change in color difference of gold colored titanium in Okinawa
in the case where conventional material and also material that
does not readily become discolored are used as base materials

Color difference

Okinawa exposure test

15

Points to note concerning titanium building material that does not readily become discolored● This technology reduces the rate of growth of the● It is considered that there is a possibility of discol-oxide film in a natural environment, and thus slows
down the speed of discoloration. It does not stop
discoloration from occurring.

oration occurring in tropical regions of hightemperature and humidity or regions where severeacid rain falls.

● Material that does not readily become discolored which● Like other metals, titanium sometimes appears discol-

was installed during or after 2000 and also material thathas been subjected to an exposure test have presently
undergone little change in the base metal or the color,and maintains a satisfactory condition.

ored due to dirt or finger marks. Contamination can beremoved by carrying out appropriate cleaning. If thecontamination is allowed to remain, it will become
difficult to remove.

11

3–2. Development of titanium that does not readily become discolored
Discoloration phenomenon
At the beginning of the 1990s, some of the titanium
roofs that had been installed prior to that time changed
color from silver to brown.

Examples of discoloration[The test piece is conventional vacuum-annealed material (VA).]

The surface of titanium has a chemically stable oxide
film (passive film). The protective action of this film
provides excellent resistance to corrosion. If the oxide filmon the surface of the titanium (thickness approx. 0.01 μm)
grows to between 0.03 and 0.05 μm, the original silver
surface will appear brown as a result of interference light.
This phenomenon is called discoloration of titanium. (Itdoes not adversely affect the corrosion resistance.)

As a result of investigating the discolored areas, aminute amount of carbide and fluorides was foundremaining in the oxide film and on the surface of thetitanium base metal. Various tests were carried out, andas a result it was found that these substances react withacid rain, causing the film to grow. The higher the atmospheric temperature, the more pronounced is this trend.

Mechanism of discoloration of titanium (pattern diagram)
Acid rain of pH 4.5 or lessTitanium carbide

Base metal (uncoated) for use as a building material may often come in delicately varied color tones. Titanium is no exception.
In order to prevent impairment of the class of the whole building by such an element, it is a common practice to use coils(panels) in the order of approximation and gradation in color to make color variations inconspicuous.
The photographs below are representative examples of reduction of color variations.
After 7 years’
exposure in Oita City

Kyushu National Museum (17,000 m 2)

Kyushu Oil Dome (32,000 m 2)

Hangzhou Grand Theatre (10,000 m 2)

Hozomon of Sensoji Temple (1,080 m 2)

Development of titanium building materials
that does not readily become discolored

It is known that carbon, the cause of discoloration,
which is included in rolling mill lubricant used for coldrolling during the manufacture of titanium, remains on thesurface of titanium, and also fluorides, which are includedin the acid solution used for pickling subsequent to coldrolling, remain on the surface of titanium. Accordingly, weestablished manufacturing technology to remove most of
the carbon and fluorides from the surface of the titanium.

Method of manufacturing titanium cold-rolled sheets(Points concerning the improvement of resistance to discoloration)

Hot rolling

Formation of passive film
containing fluorides

Annealing and pickling
Cold rolling

TiVacuum-annealed (VA) Ti

We have provided materials for a number of major properties. In the process, we have amassed
the know-how in control technologies to make products in a sufficient quantity to extensively
cover a large area, with the least possible variations in color tones between lots (coils).
In addition, we are also able to provide roofing and exterior-execution companies with information
required for lot control＊.
＊Lot control

Before exposure
to atmosphere

Mechanism of discoloration

4. Reduction of color-tone from one lot to anotherPickled (AP) Ti(Carburizing from lubricating oil)

Cleaning (Removal of adhering oil)
TiC changes to
TiO2 due to acid rain.

Vacuum annealing (Control of
the formation of titanium carbide)

Porous Ti Oxide-hyd

Pickling (Preventing the inclusionof fluorides in the surface film)

Dull finish

In order to evaluate the performance with respect to thediscoloration of the manufactured titanium, an exposure test
was carried out in Okinawa and also a discoloration accelerated test method based on the mechanism of discoloration
was developed. As a result, the effectiveness of this methodof manufacturing titanium was verified. (See Page 10.)

12

In this case, the degree of luster of the titanium has been
deliberately varied by using two kinds of alumina blasting to givethe impression of tiles.

135. A wealth of application technology[Pat. No. 3369352, No. 3362326, No. 3358699, and No. 3505036]

Distortion of the material after rolling is small, and the design performance as a roof is maintained.

Development of a material that has little distortion during forming

Development of a suitable cleaning agent● Sometimes during rolling, pocket waves occur on titanium. We have developed technology to reduce this phenomenon.

Regarding cleaning, we recommend that you use a commercially available detergent according to the manual. We have
independently developed three kinds of cleaning agent, and can introduce the manufacturer. We also have available strong
cleaning agents (Type [B] and Type [C]) for removing discoloration. Note, however, that if you use these strong cleaning agents,
the surface film will be removed as far as the base metal.

● We have succeeded in significantly reducing pocket waves by carrying out the following subsequent to vacuum annealing.

① Performing skin pass rolling by using dull rolling.
② Applying waves in advance to the edges of the titanium sheet

Kyushu National Museum(Constructed by Sanko Metal Industrial Co., Ltd.)

Shape after rolling (stepped roofing)

Example of cleaning

Developed cleaning agents
Cause of discoloration

Base
metal

Coloredtitanium

Type (A)Steel rust, dirt, etc.

○○

Type (B)

Slight discoloration(growth of the oxide film)○

×Type (C)Discoloration(growth of the oxide film)○

×Cleaning

Discolored area
※If there are places in the roof and other areas where rainwater is liable to form pools, titanium becomes contaminated like any other metal.

Contamination, if left unattended, may sometimes become hard to remove. Contamination due to drips of calking material also becomes hard to
remove with time. It is recommended that all these points be taken into consideration in the early design stages.
No edge waves ⇨ Rolling

Application of edge waves ⇨ Rolling

300

mm

Rolled cross-sectional shape
Application of edge waves ⇨ Rolling (with ribs) ⇨ Seam welding

Cleaning method

Precautions for cleaning① Removing adhesive remaining on the protective film
Wipe off adhesive using a sponge or cloth moistened with alcohol, benzene,or thinners, or a mixed solution consisting of alcohol and toluene or benzene(in sequence from the weakest acting liquid). It is important to wipe the surfaceof the titanium with an unused, clean cloth before these solvents have dried.

① There are various causes of contamination and discoloration of titanium
building material, so it is necessary to use a cleaning method that matches
the particular circumstances. Do not abruptly start cleaning the entire
surface. First carry out test cleaning on a small area, and check the removalof the contamination or discoloration. If the result of the test is satisfactory,
use that method to clean the entire surface.

② Removing contamination due to finger marks or dirt from the hands
In almost all cases, you can remove contamination using a neutral detergent orsoapy water. If you are unable to do so, use an organic solvent (alcohol,
benzene, etc.). In this case, you must observe the abovementioned precautions.
③ Removing contamination due to roofing material and concrete
Wipe away contamination using a sponge or cloth moistened with a 5%
solution of hydrochloric acid in water.

Shape after installation(welding method)④ Removing contamination due to zinc from scaffolding material
Wipe away contamination using a sponge or cloth moistened with a 15%
solution of nitric acid in water.
⑤ Removing contamination due to rainwater or dust
In almost all cases, you can wipe away contamination using a sponge or clothmoistened with a neutral detergent or an alkaline detergent. If you are unable
to do so, you may be able to remove the contamination by applying a cleaner
containing an abrasive to a soft cloth, and then rubbing gently and uniformly.
The above is a description of the various cleaning methods. In all cases,
thoroughly wash the surface with water after cleaning, and ensure that notraces of cleaning agent remain.
⑥ Removing contamination from colored titanium
Of the abovementioned cleaning methods, do not remove contamination
using hydrochloric acid, nitric acid, or a cleanser, because the film that
produces the color will be affected, preventing the surface from being
restored to its original condition.

14② When using a cleaning implement such as a cloth, sponge, loofah,scrubbing brush, cleaning brush, fine nylon pad, and so on, be sure to moveit in the direction parallel to the polishing marks on the titanium. Also, moveyour hand in such a way as to apply a uniform force as far as possible. If you
move the cleaning implement in circles, the contamination will be difficult toremove, and also the luster lines will be erased and color irregularity will
occur, marring the appearance of the titanium surface.
③ Even in the case of fairy stubborn contamination, avoid using a coarse
polishing agent, sandpaper, steel wool, or the like. Not only will this erase
the luster lines on the titanium, but also the surface will become scratched,which may cause it to become contaminated.
④ When using a commercially available cleaning reagent to remove contamination from the surface of titanium, clean not only the contaminated part but
also the vicinity as well. If you clean the titanium surface only partially,irregular color will occur, marring the appearance of the titanium.
⑤ When cleaning building tiles, marble, aluminum, and so on, if the cleaning
reagent that you used splashes on the surface of the titanium, be sure towipe away the reagent with a damp cloth. If you leave the reagent on thetitanium, discoloration may occur.
⑥ In the case of colored titanium, consult with the manufacturer prior to use.
(Source: Japan Titanium Society)15

Examples of use of titanium for building applications
Roll dull (ND20) was used in the T.C.M. (Titanium Composite Material) of Mitsubishi Plastics.

The Taipei Arena is the first instance of full-fledged use of titanium in Taiwan.

National Grand Theater (China)

Taipei Arena (Taiwan)

Surface: Roll dull (ND20)
Area: 43,000 m2
Weight: 65 tons
Completed: 2007

Surface: Roll dull (ND20)
Area: 20,000 m2
Weight: 50 tons
Completed: 2005

©Tsuyoshi Onishi

We offer particularly lustrous colored products for Frank O. Gehry’s projects

16

Hangzhou Grand Theatre (China)

Hotel Marques de Riscal (Spain)

Surface: Roll dull (ND20)
Area: 10,000 m2
Weight: 15 tons
Completed: 2003

Surface: Roll dull (SD3)
Area: 2,400 m2
Weight: 12 tons
Completed: 200417

Examples of use of titanium for building applications
The Kyushu Oil Dome is the first example of the use of titanium that does not readily become discolored. Roll dull (ND20) was used.

The teahouse of the Kinkakuji Temple, which is a World Heritage site, uses alumina blasting.

Kyushu Oil Dome

Teahouse (Josokutei)
of Kinkakuji Temple

Surface: Roll dull (ND20)
Area: 32,000 m2
Weight: 80 tons
Completed: 2001

Surface: Alumina blasting (AD03)
Area: 100 m2
Weight: 0.5 tons
Completed: 2003

JR Hakodate Station is the first structure where titanium building materials were adopted for exterior panels on a full scale, as a resultof their feature of being resistant to changes in color.

The roof of the Hozomon of Sensoji Temple was the first instance of using titanium Japanese tiles. Also, our highly workable material,
Super-Pure Flex, has been used for the ridge-end tiles.

JR Hakodate Station

Hozomon of Sensoji Temple

Surface: Roll dull (ND20)
Area: 1,000 m2
Weight: 7 tons
Completed: 2003

Surface: Alumina blasting (AD03, AD06)
Area: 1,000 m2
Weight: 8 tons
Completed: 2007
●Awarded the Fiscal 2006 Otani Art

Museum Award“Titanium stepped Japanese tile roof
and ridge-end tiles”

18

19

Titanium roofing with an alumina blasting finish adopted for the teahouse of the Raku Kichizaemon-Kan, newly opened on the premisesof the “Sagawa Art Museum” in Moriyama City, Shiga Prefecture.

Reference materials
Table 1. Orders of stabilization of metals

Order

Teahouse (Raku Kichizaemon-Kan)of Sagawa Art Museum

Orders of thermodynamic stabilization

Surface: Alumina blasting (AD03)
Area: 400 m2
Weight: 1 tons
Completed: 2007

Gold titanium used in the construction of the roof of the Miyajidake Shrine.

Miyajidake Shrine
Surface: Roll Dull (ND20), Gold coloring
Area: 220m2
Weight: 0.86tons
Completed: 2010

Table 2. Clarke number (Note)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31

Gold
Iridium
Platinum
Rhodium
PalladiumMercury
SilverCopperBismuthArsenic
CarbonLead
NickelCobaltCadmium
Iron
Tin
Molybdenum
Tungsten
Gallium
Zinc
Niobium
Tantalum
Chromium
Vanadium
Manganese
Zirconium
Aluminum
Titanium
Beryllium
Magnesium

1
Rhodium
2
Niobium
3
Tantalum
4Gold
5
Iridium
6
Platinum
Titanium
78Palladium9
Mercury
10
Gallium
11
Zirconium
12
Silver
13
Tin
14
Copper15
Beryllium
16
Aluminum17
Chromium
18
Bismuth19
Tungsten
20
Iron
21
Nickel22
Cobalt23
Arsenic
24
Carbon25
Lead
26
Cadmium
27
Zinc
Molybdenum 28
29
Vanadium
Magnesium 30
Manganese 31

Element

Existing ratio (%) Accumulated total

Oxygen
SiliconAluminum
Iron
Calcium
SodiumPotassium
Magnesium
Hydrogen
Titanium
Chlorine
Manganese
Phosphorus
CarbonSulfurNitrogenFluorine
Rubidium
BariumZirconium
Chromium
Strontium
Vanadium
NickelCopperTungsten
Lithium
CeriumCobalt
Tin

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30

Orders of practical stabilization in solution

Examples of use of titanium for building applications

49.50
25.80
7.56
4.70
3.39
2.63
2.40
1.93
0.87
0.46
0.19
0.09
0.08
0.08
0.06
0.03
0.03
0.03
0.02
0.02
0.02
0.02
0.015
0.010
0.010
0.006
0.006
0.005
0.004
0.004

O
Si
Al
Fe
Ca
Na
K
Mg
H
Ti
Cl
Mn
P
C
S
N
F
Rb
Ba
Zr
Cr
Sr
V
Ni
Cu
W
Li
Ce
Co
Sn

49.5
75.3
82.9
87.6
91.0
93.6
96.0
97.9
98.8
99.2
99.4
99.5
99.6
99.7
99.7
99.8
99.8
99.8
99.9

(Note)
Clarke Number: The ratio of elements found in the upper layer of the earth’s crust. Named after
the American geochemist F.W. Clarke (source: The Chemistry Encyclopedia Kagaku Daijiten )Titanium is the 10th most common element found in the upper layers of the earth’s crust, and interms of metals that are of practical use, it comes fourth after aluminum, iron and magnesium.

Table 3. Corrosion potential in seawater (Flow)
+0.2

0

-0.2

-0.4

-0.6

-0.8

-1.0

Platinum
Titanium
Stainless steel (SUS 304)
Nickel70/30 Copper nickel
Lead
90/10 Copper nickel
Naval brass
Aluminum bronze
Tin
9% Nickel steel
3 Chromium molybdenum steel
Mild steel
Aluminum
Zinc
Sea water-aerated atmospheric conditions (25°C)

2021