To give it its proper spec. Birmabright BB2, Produced by Birmetals
Ltd., Birmabright works, Clapgate Lane, Quinton, Birmingham. Now
defunct . This material could have also been called Hiduminium 22 ,
Alcan GB M57S , BA 21, Alcoa 510 , AWCO 21 . These being the same
thing, but produced by other companies of that era. But we only know it
as Birmabright, because thats where the factory purchased it from. Today
we know this material as NS4, or in American terms 5251. ISO
designation AlMg2. .

Zitat von repair manual 1970-1985
Body repairs, general information
1. The Range Rover body consists of a steel frame to which alloy outer panels are attached. The radiator grille, front deck panel, front wings, side door outer panels, body side outer panels, roof, rear floor and upper rear quarter panels are made from a special light magnesium-aluminium alloy known as 'Birma- bright'.

2. 'Birmabright' was developed for aircraft use, and it is much stronger and tougher than pure aluminium. It melts at a slightly lower temperature than pure aluminium and wiu not rust nor corrode under any normal circumstances. It is work-hardening, and so becomes hard and brittle when hammered, but it is easily annealed. Exposed to the atmosphere, a hard oxide skin forms' on the surface of it.
Panel beating 'Birmabright'

3. Birmabright' panels and wings can be beaten out after accidential damage in the same way as sheet steel. However, under protracted hammering the material wiu harden, and then it must be annealed to prevent the possibiJ,ity of cracking. This is quite easily done by the application of heat, followed by slow air-cooling, but as the melting point is low, heat must be applied slowly and carefully. A rough but very useful temperature control is to apply oil to the cleaned surface to be annealed. Play the welding torch on the underside of the cleaned surface and watch for the oil to clear, which it will do quite quickly, leaving the surface clean and unmarked. Then allow to cool naturally in the air, when the area so treated will again be soft and workable. Do not quench with oil or water. Another method is to clean the surface to be annealed and then rub it with a piece of soap. Apply heat beneath the area, as described above, and watch for the soap stain to clear. Then allow to cool, as for the oil method. When applying the heat for annealing, always hold the torch some little distance from the metal, and move it about, so as to avoid any risk of melting it locally.


4. Gas welding 'Birmabright'
A small jet must be used, one or two sizes smaller than would be used for welding sheet steel of comparable thickness. For instance, use a No. 2 nozzle for welding 18 swg (0.048 in.) sheet, and a 
No. 3 for 16 swg (0.064 in.) sheet.
5. The flame.should be smooth quiet and neutral, have a brilliant inner core with a well defined rounded end. The hotest point of the flame is close to the jet, and the flame should have a blue to orange envelope becoming"nearly colourless at the end.
6. A Slightly reducing flame may also be used, that is, there may be a slight excess of acetylene. Such a flame will have a brilliant inner core with a feathery white flame and a blue to orange envelope.
7. Do not use an oxydising flame, which has a short pointed inner core bluish white with a bluish
envelope.



8. Use only 5 per cent magnesium/aluminium welding rod (5 Mg/A). Sifalumin No. 27 (MG.5 Alloy) (Use Sifbronze Special flux with this rod) or a thin strip cut of parent metal - that is to say, a strip cut from an old and otherwise useless 'Birmabright' panel or sheet. Do not use too wide or thick a strip, or trouble may be experienced in making it melt before the material which is being welded.
9. Clean off all grease and paint, dry thoroughly and then clean the edges to be welded, and an area at least half an inch on either side of the weld, with a stiff wire scratch-brush or wire wool. Cleanliness is essential. Also clean the welding rod or strip with wire wool.
10. A special acid flux must be used, and we recommend 'Hari-Kari' which is obtainable from:
The Midland Welding Supply Co. Ltd.,
105 Lakey Lane,
Birmingham 28, England.
or
Sifbronze Special Flux, which is obtainable from:

Suffolk Iron Foundry (1920) Ltd., Sifbronze Works,
Stowmarket, England.
11. A small quantity of 'Hari-Kari' may be made into a paste with water, following the directions on the tin, and the paste must be applied to both surfaces to be welded, and also to the rod. In the case of Sifbronze Special Flux use in powder form as directed. Remember that aluminium and its alloys do not show 'red-hot' before melting, and so there is nothing about the appearance of the metal to indicate that it has reached welding temperature. A little experience will enable the operator to gauge this point, but a
useful guide is to sprinkle a little sawdust over the work; this will sparkle and char when the right temperature is approached; a piece of dry wood rubbed over the hot metal will sparkle at the point of contact.
12. As the flux used is highly acid, it is essential to wash if off thoroughly immediately after a weld is completed. The hottest possible water should be used, with wire wool or a scratch-brush. Very hot soapy water is good, because of the alkaline nature of the soap, which will tend to 'kill' the acid.