Emissivity Coatings

In space applications, thermal control, emissivity and asorptivity are critical factors to the optimum performance of a vehicle or satellite. Through years of research and work with various space agencies and manufacturers, TIODIZE has developed several processes and coatings to address these issues.
Tiodize Type I

Titanium anodize to control thermal radiation with solar absorbance and emittance applications.

Tiodize Type II

Resistivity is 4.5 Ohms per square inch. Can be used as an antigalling coating on titanium surfaces lubricated with oils, greases, hydraulic fluids, or in pneumatic systems.

K2V

Black emissivity coating.

Ultra VE-17

Coating to control thermal radiation with solar absorbance and emittance applications.

BK-11

High temperature version of Ultra VE-17.

K-Seal

Used on BK-11and Tiodize Type I to harden coating for high durability and handling.

IR Anodize

Used to control IR reflectance on aluminum.

emissivity

(em-uh-siv-i-tee)

The ratio of the radiation intensity from a surface to the radiation intensity at the same wavelength from a blackbody at the same temperature.

emissivity / aerospace / Black emissivity coating

TEST RESULTS

USAGE FOR THERMAL CONTROL: INSAT-1 DOMESTIC SATELLITE SYSTEM FOR INDIA

The Western Development Laboratories Division (WDL) of Ford Aerospace Communications Corporation (FACC) was chosen by the Government of India to design and build the first generation spacecraft for the Indian National Satellite System … INSAT-1. This spacecraft (shown in Figure 3-1) will introduce sociological and economical advantages of modern communications to India’s population which exceeds 613,000,000 and covers a land area measuring 3,280,483 square kilometers. INSAT-1 will provide reliable communication capability to India’s rugged terrain and inaccessible regions far more economically than any alternative high quality terrestrial system.

To accomplish the satellite’s major communications, direct broadcast satellite service, meteorology and data collection missions, it will be placed in geostationary orbit 35,784 Km above India and will employ a single 445-newton (100 pound) thruster for apogee boost. During design and development of the thruster at WDL, protection of adjacent structure against the plume was considered necessary. Titanium was the best lightweight choice for a shield, provided the thermal absorptivity/emissivity of less than 1.0 could be achieved. The TIODIZE Type I Process has these characteristics, and samples of 6Al-4V titanium were coated by TIODIZE Co., Inc. and evaluated by WDL utilizing the Gier Dunkle Source Transfer Optical System. Subsequently, preformed parts of the flight hardware were coated, and test samples were processed with the parts to verify thermal characteristics. Results of WDL tests on these test samples are presented below:

Test Sample #1 #2 #3 #4 #5
Absorptivity (as) 0.71 0.7 0.67 0.63 0.6899999999999999
Emissivity (en) 0.8 0.8100000000000001 0.83 0.85 0.82
as/en 0.89 0.86 0.8100000000000001 0.74 0.84
Test result
Absorptivity (as) 0.58
Emissivity (en) 0.89
as/en 0.65

Since the desired as/´n of less than 1.0 was achieved by the single coating, the heavier coating used to achieve the very low ratio was not used for production hardware. For additional testing, see page 12 of the Tiodize Process Booklet.

ABSORPTANCE AND EMITTANCE TESTS

Another significant use for the TIODIZE PROCESS is the control of thermal radiation. The solar absorptance (as) and normal emittance (´n) for ULTRA V-E17 and bare Type I and II TIODIZE PROCESS coatings were found to be as shown below:

AS/EN TYPE I Bare Ultra V-EI7 TYPE II BARE
(as) 0.62 0.89 0.82
(en) 0.89 0.91 0.51
Sample Description Color Emittance Adhesion
A TIODIZE Type II all over Ultra VE-17 one side No Top Coat Black 0.928 / 0.923 No Loss
B Same as A, except with Top Coat Black 0.936 / 0.934 No Loss
C TIODIZE Type I all over Ultra VE-17 one side No Top Coat Black 0.946 / 0.947 No Loss
D Same as C, except with Top Coat Black 0.95 / 0.951 No Loss
E TIODIZE Type I all over +K-seal Tan 0.932 / 0.946 Some loss on side 1 of each panel; No loss on reverse side of each panel.

The specimens were made of Titanium 6Al-4V foil, .005 inches in thickness, and TIODIZED with Type I and Type II. The ULTRA V-E17, when used, was TIODIZE® black organic coating. The absorptance was determined by the 19 point integration between 0.32 and 2.1 microns wavelength. The emittance was arrived at by a 25 point integration between 4.8 and 26.2 microns. Spectral measurements were made in either a heated Hohlraum chamber or a Gierdunkle integrating sphere with an incident angle of 20 degrees on specimens water cooled to approximately room temperature.

OPTICAL PROPERTIES FOR ION THRUSTER THERMAL COATING

Material Tiodize Ceramet KV2 TiCN TiAIN TiN
Run # 04-06-25-08-31 04-06-25-08-34 04-06-25-08-37 04-06-25-08-42
Solar Absorptance 0.9389999999999999 0.66 0.868 0.371
Infrared Emmitance 0.8100000000000001 0.21 0.6 0.09