Absorption Refrigerator Corrosion Prevention Methods
Overview of Technical Issues:
The refrigerant-absorbent solution produces harmful chemical corrosion on metal vessel walls, piping, and heat transfer surfaces throughout the absorption refrigerator system, causing progressive material degradation, wall thinning, potential leakage, contamination of the refrigerant cycle, and reduced heat transfer performance; the goal is to prevent or minimize corrosion to extend system lifespan and maintain reliable long-term operation.
Solution directions generated for this problem
Problem Direction 1 :
ImproveMetal corrosion resistance
VSConstraintMaterial and coating cost
Inspiration 1 : Cross-domain reference
Application Principle: #35 Parameter changes
Cross-domain applicability
Method of mooring floating wind turbine platforms
Innovative Solution Refine solution
Plasma nitriding surface hardening for absorption refrigerator vessels
Apply plasma nitriding to carbon steel vessels to create corrosion-resistant surface layer
How to solve :
- Treat carbon steel vessel walls and heat exchanger surfaces with plasma nitriding at 500-550°C for 8-12 hours under nitrogen-hydrogen atmosphere (N₂:H₂ = 3:1, pressure 200-500 Pa) to form 50-150 μm iron nitride diffusion layer (ε-Fe₂₋₃N and γ'-Fe₄N phases)
- Apply cathodic plasma discharge at 400-600V DC to accelerate nitrogen ion bombardment and diffusion, achieving surface hardness 800-1200 HV and corrosion resistance equivalent to 316L stainless steel without bulk material replacement
- Implement post-treatment passivation with 2-5% chromate solution for 30 minutes to seal micro-pores in nitride layer, reducing corrosion rate to below 0.02 mm/year in ammonia-water and LiBr environments while maintaining base carbon steel cost and weight
Expected Effect : Corrosion rate reduced to <0.02 mm/year; material cost increase <8%; weight unchanged; service life extended to 25+ years
Risk Control :
- nitriding depth uniformity on complex geometries
- hydrogen embrittlement risk in high-strength steels
- process control for weld seam zones
Problem Direction 2 :
ImproveSolution-material chemical compatibility
VSConstraintHeat transfer surface manufacturing complexity
Inspiration 1 : Cross-domain reference
Application Principle: #2 Taking out (Extraction)
Cross-domain applicability
Product portion enrobing machines and methods
Innovative Solution Refine solution
Chemical inhibitor dosing system for in-situ corrosion suppression
Inject corrosion inhibitor directly into refrigerant-absorbent solution
How to solve :
- Install inline dosing pump to inject corrosion inhibitor cocktail (sodium molybdate 200-400 ppm + benzotriazole 50-100 ppm) into circulating solution at absorber inlet, eliminating need for surface coatings
- Use pH-buffered inhibitor formulation (pH 9.5-10.5 for LiBr, 10.5-11.5 for ammonia-water) to form passive oxide layer on metal surfaces, reducing electrochemical corrosion rate from 0.5-2 mm/year to <0.05 mm/year
- Monitor inhibitor concentration via conductivity sensor (±2% accuracy) with automated replenishment every 500 operating hours, maintaining protective film integrity without manual intervention
Expected Effect : Corrosion rate <0.05 mm/year; 20+ year lifespan; no coating fabrication; system cost +8% vs +300% for titanium
Risk Control :
- inhibitor decomposition at high temperature zones
- concentration drift causing under-protection
- inhibitor-refrigerant chemical interaction
Problem Direction 3 :
ImproveSystem operational reliability
VSConstraintMaterial and coating cost
Inspiration 1 : Cross-domain reference
Application Principle: #11 Beforehand cushioning (Prior cushioning)
Cross-domain applicability
High-voltage device
Innovative Solution Refine solution
Sacrificial anode cathodic protection system for absorption refrigerator corrosion control
Pre-install sacrificial anode system during assembly to achieve long-term corrosion protection
How to solve :
- Install magnesium or zinc alloy sacrificial anodes (AZ63 or Zn-Al-Cd alloy) at strategic locations inside absorber and generator vessels using bolt-on mounting brackets—anodes corrode preferentially, protecting base metal electrochemically
- Position anodes at 300-500mm intervals along vessel bottom and sidewalls where LiBr or ammonia-water concentration is highest, ensuring anode-to-cathode surface area ratio of 1:200 to 1:300 for optimal current distribution
- Monitor anode consumption via ultrasonic thickness gauging every 24 months, replace anodes when residual thickness drops below 40% of original (typically 8-10 years), maintaining continuous protection without vessel replacement
Expected Effect : Corrosion rate reduced to <0.05mm/year; 15-20 year vessel lifespan; anode material cost <8% of titanium vessel alternative; zero weight penalty to structural components; system reliability improved from 3-5 years to 15+ years failure-free operation
Risk Control :
- anode passivation in low-conductivity solutions reducing protection efficiency
- uneven current distribution causing localized corrosion in shielded areas
- anode detachment from mounting brackets under thermal cycling
Problem Direction 4 :
ImproveComponent service duration
VSConstraintHeat transfer surface manufacturing complexity
Inspiration 1 : Cross-domain reference
Application Principle: #10 Preliminary action
Cross-domain applicability
PCSK9 IRNA compositions and methods of use thereof
Innovative Solution Refine solution
Pre-applied electroless nickel-phosphorus barrier coating for absorption refrigerator vessels
Apply electroless nickel-phosphorus coating during initial fabrication to extend vessel life without complex ongoing processes
How to solve :
- Deposit 50-100 μm electroless Ni-P coating (10-12% phosphorus) on all carbon steel heat transfer surfaces in single 6-8 hour immersion bath at 85-95°C, pH 4.5-5.0
- coating forms amorphous corrosion barrier reducing attack rate from 0.5-2 mm/year to <0.05 mm/year
- Post-deposition heat treatment at 400°C for 1 hour crystallizes Ni₃P phase, increasing microhardness to 900-1100 HV and sealing micro-pores
- Quality control via cross-sectional microscopy verifying uniform 50-100 μm thickness (tolerance ±10 μm), adhesion testing ≥35 MPa pull strength, and electrochemical impedance confirming corrosion current density <0.1 μA/cm² in simulated LiBr/ammonia-water environment
Expected Effect : Service life 8→22 years; corrosion rate <0.05 mm/year; one-time 8-hour process; material cost +12% vs titanium +400%
Risk Control :
- coating thickness non-uniformity in complex geometries
- phosphorus content deviation affecting corrosion resistance
- incomplete surface activation causing delamination
Problem Direction 5 :
ImproveSystem operational reliability
VSConstraintHeat transfer surface manufacturing complexity
Inspiration 1 : Cross-domain reference
Application Principle: #11 Beforehand cushioning (Prior cushioning)
Cross-domain applicability
5,10‑Methylene‑(6r)‑tetrahydrofolate hemisulfate
Innovative Solution Refine solution
Cathodic protection system with pre-installed sacrificial anode network for absorption refrigerators
Install pre-installed cathodic protection system during initial assembly using standard fabrication methods
How to solve :
- Install sacrificial anode arrays (zinc or magnesium alloy rods, 99.9% purity, Ø12-16mm) at strategic locations inside absorber and generator vessels using simple bolt-on brackets welded to carbon steel walls during standard fabrication—no specialized coating equipment required
- Connect anodes to vessel walls via low-resistance copper cables (≤0.5Ω total circuit resistance) forming galvanic couples
- anode placement density: 1 anode per 0.8-1.2 m² of wetted surface area, ensuring uniform current distribution and <0.05 mm/year corrosion rate on protected steel surfaces
- Implement reference electrode monitoring ports (silver/silver chloride type) at 3-5 locations per vessel to verify protection potential maintained at -0.85 to -1.05V vs Ag/AgCl
- replace depleted anodes every 8-10 years through access flanges without system disassembly
Expected Effect : Corrosion rate <0.05 mm/year; 15-20 year failure-free operation; fabrication time unchanged; material cost +8-12% vs unprotected carbon steel; anode replacement cost <5% of vessel replacement
Risk Control :
- anode current distribution non-uniformity in complex geometries
- electrical connection resistance drift over time
- ammonia-water conductivity variation affecting protection efficiency
Problem Direction 6 :
ImproveComponent service duration
VSConstraintMaterial and coating cost
Inspiration 1 : Cross-domain reference
Application Principle: #10 Preliminary action
Cross-domain applicability
Aerosol generating device, method for controlling same, and charging system including same
Innovative Solution Refine solution
Pre-passivation surface treatment for extended corrosion-free operation
Apply multi-stage pre-passivation treatment to carbon steel surfaces before system assembly
How to solve :
- Execute three-stage surface pre-treatment: alkaline degreasing (pH 12-13, 60°C, 15 min), phosphate conversion coating (zinc phosphate bath, 70-80°C, 10-12 min, coating weight 2-4 g/m²), followed by chromate sealing (hexavalent chromium 0.5-1.0 g/L, pH 1.8-2.2, 25°C, 3 min) to form 0.5-1.0 μm dense barrier layer
- Apply electroless nickel-phosphorus topcoat (8-10% phosphorus content, 88-92°C bath temperature, pH 4.5-5.0, 6-8 hours) achieving 40-60 μm uniform coating thickness on all wetted surfaces including complex geometries
- Perform post-deposition heat treatment at 400°C for 1 hour under nitrogen atmosphere to crystallize amorphous Ni-P structure, increasing microhardness from 500 HV to 900-1100 HV and enhancing corrosion resistance by forming stable Ni₃P phase
Expected Effect : Corrosion rate reduced from 0.5-2 mm/year to <0.04 mm/year; 20+ year lifespan achieved; material cost increase <8% vs titanium's 300-800%; weight penalty <2%
Risk Control :
- phosphate coating uniformity on complex geometries
- electroless plating bath stability and phosphorus content drift
- heat treatment atmosphere control preventing oxidation
