Films and getters · Workhorse

Vacuum black coatings

Z306values describe: Acktar Fractal Black

Space testBig science (accelerators, light sources, public fusion)

Why it wins

Emissivity and stray light are materials problems: shroud paints for radiative sinks, foil and anodize blacks for baffles, each certified for outgassing before it earns its darkness.

Why not the alternative

Ordinary black paint becomes the contamination it was meant to simulate away.

Watch out

Adhesion at cryo and particle shedding are the qualification tests, not the color.

Properties

The values below are candidate: compiled from the sources named, not yet individually validated. Provisional provenance: ECSS space product assurance standards; NASA outgassing database.

Wet cleaning

Recipe	Acktar: solvent wipe only, it is a vacuum-deposited inorganic film. Z306: do not wet-clean, recoat instead
Forbidden	anything abrasive on either; aqueous on Z306
Limit	for a black coating, any cleaning that raises reflectance has failed

Vacuum and outgassing

Vapour pressure	Z306 is a paint and behaves like one

Temperature

Vacuum degas	as bake
Metallurgical limit	Z306 binder degrades; Acktar is inorganic

Thermal

CTE	substrate
Thermal conductivity	substrate
Emissivity	0.90–0.99, which is the point

Mechanical

Strength	coating
Elongation	nil

Electrical and magnetic

Relative permeability	1.0
Resistivity	Acktar available conductive or insulating

Engineering

Corrosion	good
Joining	sprayed (Z306) or vacuum deposited (Acktar)
Process notes	stray light control and thermal emissivity in one layer
Availability and cost	Acktar and space coating suppliers

By grade

These grades differ by an order of magnitude, so their values are carried per grade and override the card.

Parameter	Aeroglaze Z306	Acktar foil blacks
Outgassing, unbaked (10 h)	1e-7 mbar·L/s/cm²	1e-10 mbar·L/s/cm²
Outgassing, baked	1e-9 mbar·L/s/cm²	5e-13 mbar·L/s/cm²
Bake, assembled	120 °C	350 °C

Grades

Aeroglaze Z306	the LN2 shroud and spacecraft PU black, E595 compliant with cure
Acktar foil blacks	etched metal blacks: no organics, baffle grade
Black anodize (Martin Black class)	aluminum baffles, watch the sealed-pore water

Sources · 2

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