Why chooose alkali resistant coating SiC heater?

Alkali resistant coating SiC heater is also called “D coating SiC heater”, it can make SiC heater last longer.

SiC heater can be used in the furnaces with different atmospheres, however, service life of SiC heater will be affected and shortened under some atmospheres.

Alkali Resistant Coating Sic Heater
Alkali Resistant Coating Sic Heater

In the actual production environment, several harmful volatiles possibly exist in some furnaces meanwhile, and even some harmless volatiles become harmful after mixed with some other volatiles, thereby affecting the service life of heater.

In order to extend the service life of heater in different atmospheres, we developed various coating to protect the SiC structure of heater to prevent rapid aging, the coatings we have mainly are:
A Coating sic heater elements,
B Coating sic heater elements,
D Coating(Alkali-resistant) sic heater elements

Specification for alkali resistant coating SiC heater:

  • Coating type: D
  • Appearance:white grey, without luster.
  • Tube Diameter:8mm to 65mm
  • Voltage:110-480v
  • Working temperature:up to 1450

Advantages of Alkali Resistant Coating of SiC heater

Alkali-resistant Coating is mainly used in atmosphere of alkali metal, under this atmosphere, alkali metal is easy to congeal on surface of heater and react with SiC on surface, thereby accelerate the aging of heater.Alkali resistant coating SiC heater will protect the heater body and prolong the service life of it.

How to choose the coating of SiC heater?

Since different coatings have different effects in different atmospheres, it’s necessary to proceed the small batch tests against the specific problem in order to find out the optimum plan and select the best coating.

After years of testing, we have developed a variety of sic heaters elements for different environments.
A Coating(Resistant to Vapor and Moisture),
B Coating(Resistant to Nitrogen gas and ammonia),
D Coating(Alkali-resistant)

Application of Alkali-resistant Coating SiC heater:

The alkali&alkaline metal oxide will react with SiC at about 1300℃ and genetate silicate, which calls alkali-chemical corrosion,and can influence the glowing of element evidently.

Atmosphere Effect Solution Recommend Coat
Vapor and Moisture Service life shortened 20% than in dry air New furnace or old furnaces not work long time, to dry at low temperature completely and then heat up A coat
Nitrogen gas Above 1400℃, nitrogen will react with SiC to form silicon nitride, elements will become fragile and service life shortened. The effect by d&ew point is same as H2 The recommended furnace temperature not higher than 1300℃, surface loading as low as possible B coat
Hydrogen The mechanical strength decreasing when elements temperature exceeds 1350℃, and also service life much depends on intensity of moisture. Operation temperature lower than 1300℃, surface loading less than 5W/ CM²
Ammonia Same as hydrogen and nitrogen Operation temperature lower than 1300℃, surface loading less than 5W/CM² B coat
Disassociated gas(Mixture of N2, CO, CO2, H2, CH4) Carbon black from decomposed hydrocarbon on elements surface will cause elements rod loose. Introducing air into furnace frequently to burn up additional Carbon. At side of furnace design, keep enough space between elements to prevent short circuit.
(S、S2) Above 1300℃, surface of elements will be corroded and resistance increasing rapidly. Keep elements temperature lower than 1300℃
Vacuum SiO2 protect film will not be formed, SiC decomposed itself and service life shortened. Using in pressure over 0.13Pa and furnace temperature under 1100℃
Others Various substances from treated materials, such as Pb, Sb, alkali metal react with elements, which may shorten elements service life. To get rid of these substances in advance, design gas outlet in furnace in order to decrease the effect. D coat

Which shape silicon-carbon heating elements can be added with alkali-resistant coating?

Coating is an additional process for silicon-carbon heating elements, and all the shapes of silicon-carbon rods that can be coated as following :

Db Type Sic Heating Elements

DB type silicon carbide heater rod

DB type silicon carbide heater rod general introduction DB type silicon carbide heater rods consist of a hot zone with high electrical resistivity and rigidly connected with two thickened cold zones of low resistance owing to their larger diameter and special manufacturing technique. The particular connecting technique ensures perfect mechanical and electrical operation. Hot zones […]
Ed Type Sic Heating Elements

ED type sic heating elements

General introduction ED type sic heating elements(also called RR type sic heating elements) is a straight rod type resistance heating element made of green silicon carbide as the main raw material, through hydraulic preliminary forming, baking, sintering and recrystallization, hot and cold end resistance cooperation and 2400 ℃ secondary sintering according to a certain proportion. […]
M Type Sic Heating Elements

M type Globar silicon carbide heating element

Why M type Globar silicon carbide heating element M type silicon carbide heating Elements look like the letter “M”, also known as W-type Globar silicon carbide heating elements, there are three heating units. How to install M type Globar silicon carbide heating element? The two cold ends of the M-type Globar Silicon Carbide heating element […]
Sg Type Sic Heating Element

SG type SiC heating elements(single spiral)

What is sg type sic heating elements? The spiral sg type sic heating elements are made of special high-density reaction-bonded silicon carbide. Advantage A spiral slot in the hot zone reduces the cross sectional area. This provides the electrical resistance ratio to make the ends cool and the hot zone hot. Special cold ends may […]
Sgr Type Sic Heating Elements

SGR type sic heater element

What is SGR type sic heater element? SGR type sic heater element similarly to Single spiral type. SGR type sic heater element is a tubular element with a spiral-grooved heating section, and as a major characteristic, both electrical connections are found at one end only. Double spiral SiC Heater Element (SGR type SiC Heater Element) […]
Slot Type Sic Heating Element

Slot type sic heating element

What is slot type sic heating element ? The slot type SiC heating element is manufactured with a spiral-grooved heating section which is made of homogeneous, high-density silicon carbide crystals. It is more resistant to heat and corrosion than conventional products. It is also able to withstand operations in rigorous conditions. Also called Ux type […]

They are all called alkali resistant coating SiC heater after D coating.

Customers can choose alkali resistant coating SiC heater according to your own furnace operating environment.