Surface Treatment Gas, Pressure & Dosing

Q: How do I stop coating thickness banding at low flow?

Use FMI valveless piston pumps for pulseless feed and an Equilibar BPR to stabilise downstream back pressure; pair with an Alicat PC for closed loop pilot control.

Q: Can one BPR handle mixed vapour/liquid streams near hot zones?

Yes—Equilibar HT/GSD variants handle mixed phases and elevated temperatures with frictionless control.

Suface Treatment - Why is Precision Flow, Pressure & Dosing important?

Surface processes live or die on stable gas delivery, repeatable back‑pressure, and pulseless liquid dosing. Small deviations trigger coating non‑uniformity, roughness, pin‑holes, over‑spray, poor adhesion or cure issues.

Fluid Metering — valveless, pulseless liquid feeds for primers, binders & precursors

Common issues

Pulsation & drift in low rate liquid feeds cause coating thickness variation and streaks.
Viscosity changes (temperature/shear) upset mix ratios and flow stability during long runs.
Frequent starts/stops & reversals introduce bubbles and dead time in small bore lines.

How Fluid Metering solves it

Valveless ceramic piston technology delivers pulseless, drift free micro flows from µL/min to L/min; only one moving part means repeatability and simple cleaning. Use QV variable speed drives with Q series pump heads for steady feeds to slot die, spray or APCVD precursor skids.
RHV/RHB low flow modules give instant, linear adjustment at very low rates for R&D or additive tint/colour dosing.

Alicat — fast, accurate gas mass flow & pressure control for plasma/CVD and vacuum coaters

Common issues

Sub sccm to slpm gas control with fast recipe pulsing (APCVD, plasma polymerisation) without overshoot.
Vacuum operation & positive shut off to protect chamber integrity and avoid backstreaming
Flow errors when back pressure or temperature shifts during pump/purge or throttle valve moves.

How Alicat solves it

The Alicat MC and Alicat MCV MFCs use laminar differential pressure sensing with integrated P&T compensation for 50–100ms control response and broad turndown—excellent for fast pulses and low flows on plasma/CVD steps. The MCV adds a helium tight positive shut off (≤1×10⁻⁹ atm cc/s He) and metal face‑seal connections for vacuum coaters.
Alicat PC/PCS/PCD pressure controllers stabilise chamber or line pressure (single or dual valve), decoupling flow pressure interactions that cause overshoot and thickness swings.
For high pressure or corrosive service (e.g., reactive gases), use MCQ/MCS variants; for ultra low ΔP into sensitive plasma tools, consider MCW (Whisper).

Equilibar — ultra stable back pressure for exhaust, recirculation & mixed phase streams

Common issues

Back pressure fluctuations in APCVD exhaust or liquid recirculation loops cause coating non uniformity and cure defects.
Conventional spring BPRs show hysteresis and struggle with mixed phase/condensable flows or very low rates.
High temperature locations (near hot coaters/ovens) require robust materials and diaphragms.

How Equilibar solves it

Dome loaded, multi orifice BPRs provide frictionless, fast control with exceptional resolution at ultra low to high flows—stable even with mixed phases. See General Service (GSD) for ¼″–1″ lines and BD Series for 1½″–4″ high flow headers.
For high temperature service, the HT series spans materials/diaphragms to ~700°C; for vacuum distribution, the EVR Series keeps setpoint steady with minimal hysteresis. The Research Series suits benchtop trials.
Pair an Alicat PC as the electronic pilot with an Equilibar BPR to achieve closed loop precision from vacuum to positive pressure.

Surface Treatment Application Selection Guide

Application	Recommended Technologies	Why It Helps
Vacuum coating process (CVD, PVD)	Alicat M/MCV Series Meter & Controller	Precise mass‐flow control and vacuum measurement help maintain uniform coating thickness and process repeatability.
Thermal spray / plasma spray deposition	Alicat High Temperature HT Series + CODA Coriolis High-Accuracy Flow Meter	Handles high temperature gas flows and accurately measures the carrier and cooling gases for consistent spray deposition.
Flame flash / surface activation of substrate	Alicat PC/PC3 Pressure Controller + Research Series Flow Meter	Handles high temperature gas flows and accurately measures the carrier and cooling gases for consistent spray deposition.
Flame flash / surface activation of substrate	Alicat PC/PC3 Pressure Controller + Research Series Flow Meter	Allows control of back-pressure and mass flow for flame jets, ensuring uniform substrate activation before coating.
Plasma polymerisation of textiles/materials	Alicat M Series Meter (Anti-Corrosive) + PCR/PC Pressure Controller	Corrosion-resistant sensors manage reactive plasma gases and pressure, delivering stable polymer layers on complex shapes.
Painting / wet chemical surface treatment	Alicat General Service GSD or BD Series + FMI Variable Speed Pump	Enables fine monitoring of solvents and spray air plus pump control for consistent film thickness and surface finish.
Vacuum infiltration or degassing of porous components	Alicat EVR Series Vacuum Meter + CODA Coriolis Controller	Measures low vacuums and mass flow of infiltration media, improving impregnation and bond strength of treated surfaces.