Volatilizable frit composition forming oxidation-inhibiting vapors

Claim 2

A frit composition adapted to be applied to a metal substrate containing iron and fired to form a ceramic coat, said frit composition comprising (a) in major amount a primary devitrifiable frit composition adapted to fuse at a firing temperature and upon cooling form devitrified particles, and (b) in minor amount a secondary frit composition containing a volatilizable metal oxide adapted to form at a firing temperature a substantially amorphous glass and precipitate crystals of said volatilizable metal oxide partially to volatilize said precipitated crystals at said firing temperature, thereby to provide protective vapors effective to inhibit oxidation of said substrate, and upon cooling to form an amorphous bond adhering said devitrified particles of the primary frit composition one to another, said volatilizable metal oxide being selected from the oxides of antimony, tin, vanadium, molybdenum, lead, arsenic, and mixtures thereof, the combination of said devitrifiable primary and amorphous secondary frit compositions providing a balanced, controlled release of the metallizable metal oxide at the time of firing to extend the protection afforded by the volatilizable metal oxide over a period of time.

Claim 3

The frit composition of claim 1 in which said secondary frit composition contains about 14% to about 50% by weight of fluxing agents.

Claim 4

The frit composition of claim 1 in which said secondary frit composition contains from about 30% to about 50% by weight of fluxing agents.

Claim 5

The frit composition of claim 1 in which said secondary frit composition contains from about 9% to about 80% by weight of said volatilizable metal oxide.

Claim 6

The frit composition of claim 1 in which secondary frit composition comprises from about 10% to about 45% by weight of said primary frit composition.

Claim 7

The frit composition of claim 1 in which said firing temperature is within the range of about 1300° F to about 1700° F.

Claim 8

The frit composition of claim 1 in which said secondary frit composition consists essentially of per 100 parts: ______________________________________ Component Parts by Weight ______________________________________ Volatilizable Metal Oxide 9 to 80 SiO.sub.2 0 to 35 B.sub.2 O.sub.3 0 to 40 Na.sub.2 O 0 to 40 K.sub.2 O 0 to 25 CaO 0 to 30 Al.sub.2 O.sub.3 0 to 30 BaO 0 to 40 ZnO 0 to 25 F.sub.2 0 to 10 ______________________________________ the fluorine being present as the fluoride of at least one of the metals indicated.

Claim 9

The frit composition of claim 1 in which said volatilization metal oxide is an oxide of antimony.

Claim 10

The frit composition of claim 1 in which said primary frit composition is adapted to form a porous ceramic coat upon said firing and cooling.

Claim 11

The frit composition of claim 1 in which said primary frit composition is adapted to form a porous ceramic coat upon said firing and cooling and contains an oxidation catalyst.

Claim 12

The frit composition of claim 1 in which said primary frit composition is adapted to form a porous ceramic coat upon said firing and cooling and contains an oxidation catalyst in an amount to form about 10% to about 70% by weight of said ceramic coat, the oxidation catalyst being at least one metal oxide selected from a group consisting of the oxides of cobalt, manganese, copper, and chromium.

Claim 13

The frit composition of claim 1 in which said primary frit composition is adapted to form a porous ceramic coat upon said firing and cooling and contains an oxidation catalyst in an amount to form from about 15% to about 70% by weight of said ceramic coat, the oxidation catalyst consisting essentially of iron oxide.

Claim 14

In a process for forming a ceramic coat over a metal substrate containing iron by applying a frit composition thereover and firing, the improvement of inhibiting oxidation of said substrate during the firing by using combined frit compositions comprising (a) in a major amount a primary devitrifiable frit composition adapted to fuse at a firing temperature and upon cooling form devitrified particles, and (b) in minor amount a secondary frit composition adapted to form at a firing temperature a substantially amorphous glass, firing said primary and secondary frit compositions, forming an amorphous glass from said secondary composition, precipitating crystals of said volatilizable metal oxide from said amorphous glass, at least partially volatilizing said crystals to provide protective vapors effective to inhibit oxidation of said substrate, forming devitrified particles from said primary composition upon cooling, and using said amorphous glass to bond said devitrified particles one to another, said volatilizable metal oxide being selected from the oxides of antimony, tin, vanadium, molybdenum, lead, arsenic, and mixtures thereof, the combination of said devitrifiable primary and amorphous secondary frit compositions providing a balance, controlled release of the volatilizable metal oxide at the time of said firing to extend the protection afforded by the volatilizable metal oxide over a period of time.

Claim 15

In a process for forming a ceramic coat over a metal substrate containing iron by applying a frit composition thereover and firing, the improvement of inhibiting oxidation of said substrate during the firing by using combined frit compositions comprising (a) in a major amount a primary devitrifiable frit composition adapted to fuse at a firing temperature and upon cooling form devitrified particles, and (b) in minor amount a secondary frit composition adapted to form at a firing temperature a substantially amorphous glass, firing said primary and secondary frit compositions, forming an amorphous glass from said secondary composition, precipitating crystals of said volatilizable metal oxide from said amorphous glass, at least partially volatilizing said crystals to provide protective vapors effective to inhibit oxidation of said substrate, forming devitrified particles from said primary composition upon cooling, and using said amorphous glass to bond said devitrified particles one to another, said volatilizable metal oxide being selected from the oxides of antimony, tin, vanadium, molybdenum, lead, arsenic, and mixtures thereof, the combination of said devitrifiable primary and amorphous secondary frit compositions providing a balance, controlled release of the volatilizable metal oxide at the time of said firing to extend the protection afforded by the volatilizable metal oxide over a period of time.

Claim 16

The process of claim 13 in which said secondary frit composition contains about 14% to about 50% by weight of fluxing agents.

Claim 17

The process of claim 13 in which said secondary frit composition contains from about 30% to about 50% by weight of fluxing agents.

Claim 18

The process of claim 13 in which said firing is within the range of about 1300° F to about 1700° F.

Claim 19

The process of claim 13 in which said secondary frit composition consists essentially per 100 parts of: ______________________________________ Component Parts by Weight ______________________________________ Volatilizable Metal Oxide 9 to 80 SiO.sub.2 0 to 35 B.sub.2 O.sub.3 0 to 40 Na.sub.2 O 0 to 40 K.sub.2 O 0 to 25 CaO 0 to 30 Al.sub.2 O.sub.3 0 to 30 BaO 0 to 40 ZnO 0 to 25 F.sub.2 0 to 10 ______________________________________

Claim 20

The process of claim 13 in which said volatilizable metal oxide is an oxide of antimony.

Claim 21

The process of claim 13 in which said secondary frit composition comprises from about 10% to about 45% by weight of said primary frit composition.

Claim 22

The process of claim 13 in which firing and cooling said primary frit composition forms a porous ceramic coat, and at least one of said primary and secondary frit composition contains an oxidation catalyst.

Claim 23

The process of claim 13 in which firing and cooling said primary frit composition forms a porous ceramic coat and said primary frit composition contains an oxidation catalyst in an amount to form from about 10% to about 70% by weight of said ceramic coat, the oxidation catalyst being at least one metal oxide selected from the group consisting of the oxides of cobalt, manganese, copper and chromium.

Claim 24

The process of claim 13 in which firing and cooling said primary frit composition forms a porous ceramic coat, and said primary frit compositions contains an oxidation catalyst in an amount to form from about 15% to about 70% by weight of said ceramic coat, the oxidation catalyst consisting essentially of iron oxide.

Claim 25

The process of claim 13 in which said secondary frit composition contains from about 9% to about 80% by weight of said volatilizable metal oxide.

Claim 26

The process of claim 13 in which firing said primary frit composition forms a porous ceramic coat.

Claim 27

The process of claim 13 in which said firing is at least as high as 1480° F for at least three minutes.