Inkjet printer having printhead and ink for minimizing corrosion of exposed corrodible structures within printhead

1. An inkjet printer comprising:

an inkjet printhead comprising at least one corrodible structure comprised of silicon nitride, borophosphosilicate glass (BPSG) or silicon oxide, said corrodible structure having a surface exposed to ink; and

an ink reservoir containing said ink, said ink reservoir being in fluid communication with said printhead,

wherein said ink comprises:

water;

an azo dye comprising one or more sulfonate groups and a potassium counterion; and

an Al(III) metal additive for minimizing corrosion of said exposed surface.

2. The inkjet printer of claim 1 , wherein said metal additive comprises aluminium nitrate nonahydrate.

3. The inkjet printer of claim 1 , wherein said metal additive is contained in said ink in a concentration in the range of 0.01 to 200 ppm.

4. The inkjet printer of claim 1 , wherein said ink comprises 0.01 to 25 wt. % of said dye.

5. The inkjet printer of claim 1 , wherein said printhead comprises a plurality of nozzle chambers, each nozzle chamber comprising at least one structure comprised of silicon nitride.

6. The inkjet printer of claim 5 , wherein a roof of each nozzle chamber defines part of a nozzle plate for said printhead, wherein said nozzle plate is comprised of silicon nitride.

7. The inkjet printer of claim 1 , wherein said printhead comprises a plurality of nozzle chambers, each nozzle chamber comprising at least one structure comprised of silicon oxide.

8. The inkjet printer of claim 1 , wherein said printhead comprises CMOS layers having at least one layer of BPSG exposed to said ink.

9. The inkjet printer of claim 1 , wherein said printhead comprises CMOS layers, having at least one layer of silicon oxide exposed to said ink.

10. The inkjet printer of claim 8 , wherein said printhead comprises a plurality of ink inlets defined by openings through said CMOS layers.

11. A method of minimizing corrosion of at least one corrodible structure in a printhead, the corrodible structure being comprised of silicon nitride, borophosphosilicate glass (BPSG) or silicon oxide, the method comprising exposing a surface of the corrodible structure to an ink comprising:

water;

an azo dye comprising one or more sulfonate groups and a metal counterion; and

an Al(III) metal additive for minimizing corrosion of said exposed surface,

wherein an amount of Al (III) additive required to minimize corrosion by dyes absent potassium counterions is less than an amount of Al (III) additive required to minimize corrosion by dyes comprising potassium counterions.

12. An ink set comprising a plurality of different colored inks, each ink of the ink set comprising:

water; and

an azo dye having one or more sulfonate groups and a metal counterion,

wherein one or more of the inks comprises an Al(III) metal additive,

and wherein a first ink absent a potassium counterion comprises less Al(III) additive than a second ink comprising a potassium counterion.