Batumi air carries salt every day of the year. Combined with 76-89% humidity peaks and persistent maritime exposure, every metal surface within 2 km of the coast lives in a continuous low-level electrolytic environment. That means materials don't fail randomly — they fail predictably, on a clock you can calculate. The choice between cheap-now and durable-now isn't sentimental; it's quantifiable. Below, the chemistry and the math.
The corrosion mechanism — chemistry first
Salt (NaCl) dissolves in atmospheric humidity to form a conductive electrolyte film on metal surfaces. Where two different metals contact each other (galvanic coupling), or where the same metal has imperfect surface (oxide layer breaks), an electrochemical reaction begins: electrons flow from the more reactive metal to the less reactive one, dissolving the surface. On standard steel, this is ordinary rust — Fe₂O₃ formation visible within 6-12 months. On unprotected aluminum, you get pitting corrosion — small holes that grow inward. Even PVC, which doesn't 'rust', hydrolyzes in salt + UV — polyamide-filled hardware embrittles within 5 years.
Material grades — what works on the coast
Standard low-carbon steel: 6-12 months to visible rust. Galvanized steel: 3-7 years before zinc layer depletes. Powder-coated steel: 5-10 years before chip-induced rust appears. Bare aluminum (mill finish): 5-15 years to surface oxidation that becomes structural. Anodized aluminum: 30+ years with no maintenance. Stainless A2 (304): 10-15 years before pitting in coastal exposure. Stainless A4 (316): 30+ years. The progression is non-linear — anodizing isn't 2x better than bare aluminum, it's 4-5x better, because it changes the failure mode entirely.
Anodizing — what it actually is
Anodizing is an electrochemical process that thickens aluminum's natural oxide layer from ~5 nanometers (natural) to ~15-25 micrometers (anodized) — a 3,000x increase. The new surface is Al₂O₃ — chemically identical to ceramic, completely inert to salt and most acids. Importantly, anodizing is not a coating applied on top — the oxide grows from within the metal, so it can't chip or peel. Color is added during anodizing by depositing pigment in the oxide pores, then sealing them — color is integral to the surface, not a paint over it.
A4 vs A2 stainless — the molybdenum difference
Stainless steel resists corrosion via a thin chromium oxide film. A2 (Type 304) contains 18% chromium, 8% nickel — adequate for normal indoor and dry outdoor environments. A4 (Type 316) adds 2-3% molybdenum — and that addition specifically resists chloride-ion attack (the salt in salt air). The difference is dramatic on the coast: A2 hardware will pit and discolor within 3-5 years, while A4 lasts 30+. The cost difference is ~30-40% on hardware components — small relative to the lifecycle gap.
Anodizing vs. powder coating — when each makes sense
Powder coating applies pigmented polymer (typically epoxy or polyester) electrostatically and bakes it on. Result: a protective coating ~60-100 micrometers thick. Pros: vivid color range (any RAL spec), lower cost (~30-50% cheaper than anodizing). Cons: it's a coating — chip exposes the bare metal, and chips happen during installation, transport, weather. Once chipped, the exposed spot corrodes preferentially. Anodizing has no chip risk because the protective layer is structural. For inland Tbilisi or sheltered installations, powder coating is fine. For Batumi coastal exposure, anodizing is the right choice every time.
Real cost over 20 years
Take an 8 m² balcony at the lowest tier. Standard hardware + bare aluminum: install $1,200, hardware fails year 5 ($300 replacement labor), profile pitting visible year 10, full replacement year 12 ($1,400). 20-year cost: $2,900, plus 8 weeks total downtime in repairs. Premium tier (anodized + A4): install $2,400, no hardware service needed, courtesy maintenance year 10, profile still good at year 25. 20-year cost: $2,400, ~zero downtime. The 'expensive' Premium is actually cheaper over the timescale that matters.
What we install at each tier
Standard ($135-180/m²): bare aluminum profiles, A2 stainless hardware. Acceptable for sheltered installations >2 km from coast. Premium ($220-320/m²): anodized aluminum profiles, A4/316 stainless hardware on all visible and load-bearing fixtures, EPDM gaskets (UV-resistant). The recommended baseline for Batumi addresses. Signature ($400+/m²): same as Premium plus marine-grade silicone sealants, optional powder-coated overlays for color matching, courtesy annual maintenance visits for the first 5 years included.
Maintenance protocols for coastal installations
Annual: rinse exposed metal surfaces with fresh water (not just rain — actively rinse). Inspect gaskets for compression set and replace at 5-year intervals. Lubricate moving hardware (rollers, hinges) with marine-grade silicone grease. Clean glass with non-acidic cleaner — acidic cleaners damage anodized layer over time. We include the first annual visit on Premium+; subsequent visits are paid (~$80-150 per visit) but rarely needed if the system was specified correctly.