Abstract: The invention relates to electric incandescent lamps having a gas fill containing halogen. The internal surface of the lamp envelope and optionally also the exposed surface of internal components of the lamp are protected from attack by halogens including fluorine by a continuous imperforate coating composed of a metal oxide resistant to halogen attack. In order to achieve the necessary degree of continuity of the coating the oxide is formed in situ from a compound of the metal deposited as a solution on the surface. The preferred oxide is alumina, the other oxides of polyvalent and transition metals, including metals of the lanthanide series may be used. The coatings are preferably formed from solutions of halides of the metals in polar organic solvents such as methanol. The invention prolongs the life of lamps provided with the protective coating and enable such resistant and possibly cheaper materials to be employed for certain lamp components.

Abstract: Electric discharge lamps of extended life can be produced or cheaper materials used in their manufacture by providing on the internal surface of the envelope and on the exposed surfaces of internal components a protective coating of a metal phosphate or arsenate glass. External surfaces can also be protected against corrosion in air or in the atmosphere within an outer jacket, where this is employed. The coating may be applied in a liquid medium which, preferably after draining, is warmed to evaporate the medium and thereafter baked to form the vitreous coating.

Abstract: Tungsten-halogen lamps of extended life are obtained by coating internal surfaces of the discharge tube and exposed surfaces of internal components with metal phosphate or arsenate glasses. The preferred glass is aluminium titanium phosphate. The coatings may be formed by applying a liquid composition capable of generating the desired phosphate or arsenate to the surfaces to be coated, and subsequently heating them to remove the liquid medium and form a vitreous coating. The medium may be water or an organic solvent such as an alcohol, and may contain a dissolved compound of the metal and an oxyacid of phosphorus or arsenic.

Abstract: Electric discharge lamps of extended life can be produced or cheaper materials used in their manufacture by providing on the internal surface of the envelope and on the exposed surfaces of internal components a protective coating of a metal phosphate or arsenate glass. External surfaces can also be protected against corrosion in air or in the atmosphere within an outer jacket, where this is employed. The coating may be applied in a liquid medium which, preferably after draining, is warmed to evaporate the medium and thereafter baked to form the vitreous coating.