Pure Nickel and steel type 316 filters for gas supply

The materials chosen for the aggressive gas supply systems should be corrosion resistant and intact from catalysis. The reactive gases may interact with the system materials to develop corrosive deposits that may affect the gas stream on the base of their corresponding vapour pressure. In order to confirm the application of ultra high purity gases, emphasis is on the choice of perfect materials for the development of supply unit.

Commonly stainless steel type 316l is used in the development of parts for supply of aggressive gases. An ideal choice of the stainless melt can enhance corrosion prevention in the systems. It is essential to state the suitable compositions, grain size and additions. Moreover the material used for the development, polish and electropolish are also assessed. A cautious choice of SS type 316l in the construction of filter parts is crucial as the components of similar chemistry can offer unlike performance.

It is found that difference in the corrosion performance of steel grades with high magnitudes is almost equivalent in HCL media.  In case of moisture lower than 1ppmv, bromine in HBr is not included far from the SS 316 and wide cracking of the metal is not noticed. HBr containing below 0.5 ppm moisture doesn’t affect steel component. An extreme bromide layer was observed when moisture content is about 1,000 ppm.

Corrosion is usually specified by methods for example trace gas analysis, variation of surface morphology, particle drop and leakage. The service of Steel 316 tubing is evaluated in HCl media with moisture of 1ppm for about two to three years depended on particle dropping resulted by corrosion.

Different maintenance particles are preferred to discard the dampness in the aggressive gas supply system. It has been found that if suitable purge and evacuation processes are followed to discard attacking gases, Steel 316l can interact with damped air without losing the base surface quality. Although if evacuation is not made, iron and bromine based crystalline accumulations can be made on the surface.

So to retain the purity of corrosive gases, advanced development materials are evaluated instead SS 316l. Another material tested is nickel mesh that is also intact in the diverse severe media. Although, nickel is an active metal that is employed in hydrogenation catalysis.

The heat cracking characteristics of special gases on the different metal material surfaces were evaluated which include Nickel, oxidized stainless steel 316l and chromium secured SS 316l and electropolished SS316l. The heat cracking of the special gases was evaluated through gas chromatograph.

For phosphine, this gas in 100 ppm with argon moved through the tube at the speed of 5 sccm. Nickel showed powerful catalytic effect on the phosphine cracking. The surface of nickel metal decreased phosphine content to unnoticeable levels up to 55oC. On the other hand, SS 316l showed the full heat decomposition of phosphine gas up to 260oC. Steel passivated by chromium showed the full heat cracking up to 370oC.

Additionally the catalytic influence of nickel filter on the heat cracking of silane is evaluated. Silane gas in 1000 ppm in argon was flown through the nickel mesh filter at a speed of 5 sccm. In the beginning the gas flowed at room temperature. The gas was not found at the filter exit for 2.5 hours. Thereafter it was found and silane magnitude increased to 800ppm.

A 1000 ppm silane was not found after 330 minutes refers that the catalytic degrade of silane occurred continuously. By raising the temperature up to 100oC, big spike was noticed in the hydrogen content because of further degradation of silane. Additional testing of silane with nickel filters, generaly actual follow conditions refers that nickel surface is quickly saturated and that nominal heat cracking of the gas occurs subsequent the surface saturation.

The outcomes for nickel surfaces refer that due consideration should be given to the corrosion resistant and catalytic characteristics of a material while choosing materials for service in the presence of reactive gases.

Stainless steel 316l and Nickel metal services in the aggressive gas media

The corrosion resistance offered by gas filter system of nickel and stainless steel 316l media is evaluated. The materials were exposed to HCl for 6 hours. The filter components were exposed to static HCl for around 18 hours and the process was repeated over the week. Then they were exposed to arid nitrogen for two hours after eight days. It was found that no particulate attacking products were developed during the period of HCL exposure to nickel and stainless steel components.

As nickel prevents attack so it was certain that there would be no development of corrosive materials. From the outcomes it was found that 316l stainless steel prevents attack in the conditions of ultra highly pure special gas supply units.

Electropolished stainless steel is sensitive to severe corrosion resulted by halogen based gases, particularly in weld regions. The major corrosion types are intergranular attack, general surface corrosion and pitting attack. The corrosion magnitude is widely accelerated by several inclusions, availability of volatile contaminants and carbon and sulphur content.

Nickel mesh is found to be fully intact from corrosion. The absence of particle corrosion side products found from the particle cleanliness testing, is in correspondence of corrosion resistant weld regions noticed. The perfect choice of raw materials blended with refined development techniques firmly affect the corrosion resistance of stainless steel.

Sintered woven stainless steel 316l mesh supports layers of filter assembly and nickel mesh support layers of the filter system with nickel media exposed to HCl exposure shown no corrosion.

Sintered stainless steel 316l mesh filter components are exposed to HCL and their performance is evaluated. Some level of scaling is occurred however no cracking of the mesh. Similarly, the sintered nickel mesh of the media is allowed to handle HCl gas, no damage is found after the exposure to moist HCl.

It is found that Stainless steel type 316l and nickel wire mesh prevented corrosion in the general service media that occur in corrosive gas supply system. For special gases for example phosphine and silane, no damage occurred in the mesh filter materials in the corrosive gas service for about two years. There was no corrosion or damage of the filter materials. So they are fit for use in handling the aggressive gases.