Rust Prevention

Part of Pigments and Paint

Paints and coatings for preventing rust and corrosion on iron and steel.

Why This Matters

Iron and steel are the backbone of any post-collapse infrastructure — tools, fasteners, structural supports, cookware, weapons, agricultural implements, water systems, and machinery all depend on ferrous metals. But iron rusts. Exposed to moisture and air, iron converts to iron oxide (rust) at a rate that can destroy a tool in months or consume a structural member in a few years. In a rebuilding scenario where every piece of metal is irreplaceable, rust prevention is not maintenance — it is survival.

The chemistry of rust is simple: iron + water + oxygen = iron oxide. Preventing any one of these three from reaching the metal surface stops corrosion entirely. Coatings work by creating a physical barrier between the metal and its environment. The right coating on the right surface can extend iron’s useful life from years to decades.

Every historical metalworking culture developed rust-prevention techniques because the alternative — constantly re-forging corroded tools and rebuilding failed structures — wastes fuel, labor, and increasingly scarce metal. A community that masters rust prevention stretches its metal supply by an order of magnitude.

Understanding Rust

The Corrosion Process

Rust formation is an electrochemical reaction that requires three things simultaneously:

1. Iron (the metal surface)
2. Water (even humidity is sufficient — liquid water accelerates the process)
3. Oxygen (from air dissolved in water)

If you remove any one of these, corrosion stops. Coatings work primarily by excluding water and oxygen. Some advanced coatings also create electrochemical conditions that actively prevent the iron from reacting.

Types of Corrosion

Type	Appearance	Cause	Severity
Uniform rust	Even orange-brown layer	General moisture exposure	Moderate — easy to treat
Pitting	Small deep holes in metal	Localized moisture trapping	Severe — metal thinning
Crevice corrosion	Rust in joints and overlaps	Water trapped in tight spaces	Severe — hidden damage
Galvanic corrosion	Rapid rust where two metals touch	Electrochemical reaction between dissimilar metals	Severe — preventable by isolation

Corrosion Rates

Unprotected iron in different environments:

Environment	Annual Metal Loss	Tool Lifespan Without Coating
Dry indoor	0.01-0.05 mm/year	20+ years
Humid indoor	0.05-0.1 mm/year	10-15 years
Outdoor, temperate	0.1-0.3 mm/year	3-8 years
Coastal/marine	0.3-1.0 mm/year	1-3 years
Submerged	0.1-0.3 mm/year	3-8 years

A 2mm thick knife blade in outdoor use can rust through in under 10 years without protection.

Surface Preparation

No coating works on a rusty surface. Surface preparation is more important than the coating itself.

Removing Existing Rust

1. Mechanical removal: Scraping with a blade, wire brushing, sanding with sandstone or emery cloth. Remove all visible rust and loose scale
2. Vinegar soak: Submerge rusted items in vinegar (acetic acid) for 12-48 hours. The acid dissolves rust but does not attack sound metal significantly. Scrub with a stiff brush after soaking
3. Electrolytic cleaning: If you have a battery or generator, connect the rusted item as the cathode in a washing soda (sodium carbonate) solution. Rust migrates off electrically
4. Molasses soak: Dilute molasses 1:10 in water. Soak for 1-2 weeks. The chelating acids gently remove rust. Slow but effective for delicate items

Post-Cleaning Treatment

After rust removal, the bare metal is extremely vulnerable — it will begin rusting within hours in humid air.

1. Rinse in clean water to remove acid or cleaning residue
2. Dry immediately and completely — use heat (warming by fire) if possible
3. Apply coating within 2-4 hours of cleaning
4. If you cannot coat immediately, apply temporary tallow or grease coating

Oil-Based Rust Prevention Coatings

Red Ochre Primer

The most effective and historically proven anti-rust coating from simple materials:

Why it works: Red ochre (iron oxide) pigment is already fully oxidized iron — it cannot rust further. When ground into linseed oil, it forms a dense, impermeable barrier that blocks water and oxygen. The iron oxide particles also fill microscopic pores in the metal surface.

Recipe:

• 100g finely ground red ochre
• 35-40 ml boiled linseed oil
• 15-20 ml turpentine

Application:

1. Mull ochre into oil on a flat slab until perfectly smooth
2. Thin with turpentine for the first coat
3. Apply to clean, dry metal with a brush
4. Allow to dry for 3-5 days (full cure takes 2 weeks)
5. Apply a second coat, less turpentine this time
6. Apply a third coat with minimal turpentine for maximum barrier thickness

Historical Proof

Red ochre oil paint was the standard anti-corrosion coating for iron structures, ships, and bridges for centuries. The Forth Bridge in Scotland — completed in 1890 — was protected with red oxide primer throughout its life.

Lamp Black Paint

Carbon black in oil provides excellent rust protection as a topcoat over primer:

• 50g lamp black (soot)
• 60-70 ml linseed oil (lamp black absorbs much more oil than ochre)
• Turpentine to adjust consistency

Apply over a dried red ochre primer coat for a two-layer system: iron oxide barrier + carbon barrier.

Boiled Linseed Oil (Clear)

For items where the natural metal appearance is desired:

1. Warm boiled linseed oil to 40-50C
2. Apply to clean metal with a brush or rag
3. Wipe off excess after 15 minutes
4. Allow to dry for 2-3 days
5. Apply 3-4 coats

Clear oil provides moderate protection — less than pigmented paint because it lacks the UV-blocking and barrier-thickening effects of pigment. Best for indoor tools and hardware.

Non-Paint Methods

Hot Blackening (Controlled Oxidation)

Creating a controlled oxide layer on iron that prevents further rusting:

1. Heat the iron piece to blue-hot (about 300C) — the surface turns blue-black
2. Immediately quench in oil (linseed oil works well)
3. The oil is thermally polymerized onto the hot surface, creating a tough, dark coating
4. Repeat 3-5 times for deeper protection
5. This is essentially the “seasoning” process used on cast iron cookware

Advantages: Very thin coating; does not change dimensions; suitable for precision items Limitations: Moderate protection only; needs periodic re-oiling

Wax and Grease Barriers

For tool storage and items not in active use:

Tallow coating:

• Render animal fat to produce clean tallow
• Melt and apply warm to clean metal with a cloth
• Creates a thick, water-repellent barrier
• Effective for 3-12 months depending on conditions
• Must be wiped off before use

Beeswax coating:

• Melt beeswax and apply to warm metal (heat metal gently by fire)
• Buff with a cloth after cooling
• More durable than tallow, pleasant smell
• Good for long-term storage

Lanolin (wool grease):

• Extract from raw wool by boiling fleece and skimming the grease
• Apply to metal surfaces
• Excellent long-term corrosion inhibitor — lanolin coatings can last years
• Used historically for firearm and military equipment preservation

Tar Coating

For structural ironwork not requiring a refined finish:

1. Thin pine tar with turpentine (3:1 tar to turpentine)
2. Apply hot to clean metal
3. Very thick, durable barrier
4. Ugly (black, rough texture) but extremely effective
5. Best for chain, anchor, structural bolts, underground metal, and marine hardware

Design Strategies for Rust Prevention

Coating alone is not enough. Design choices dramatically affect corrosion rates:

Eliminate Water Traps

• Drain holes: Every enclosed metal structure should have drain holes at the lowest point
• Slopes: Metal surfaces should slope so water runs off rather than pooling
• Ventilation: Enclosed metal spaces need air circulation to prevent condensation

Isolate Dissimilar Metals

When two different metals touch in the presence of moisture, galvanic corrosion occurs — one metal corrodes rapidly while protecting the other. Prevent this by:

• Placing a non-metallic barrier (leather, wood, wax, paint) between dissimilar metals
• Using fasteners of the same metal as the structure
• Avoiding copper-iron contact especially — copper accelerates iron corrosion dramatically

Accessibility for Maintenance

• Design structures so all metal surfaces can be inspected and recoated
• Avoid embedding metal in masonry where it cannot be maintained
• Use removable fasteners where possible so components can be removed for re-coating

Coating Selection Guide

Application	Primary Coating	Maintenance Interval
Hand tools (axes, saws, hammers)	Hot blackening + wax	Re-wax monthly
Kitchen/cooking ironware	Seasoning (oil burn-in)	Re-season as needed
Structural ironwork (beams, brackets)	Red ochre primer + oil topcoat	Inspect annually, recoat every 5-8 years
Nails and fasteners	Hot-dip tallow or oil coating	Not maintainable — use oil-coated when installing
Chains and cables	Tar coating	Recoat every 2-3 years
Agricultural tools (plows, hoes)	Boiled linseed oil	Re-oil after each use (soil is abrasive)
Stored reserves (spare metal)	Tallow or lanolin wrap	Check every 6 months
Water-contact items (pumps, pipes)	Red ochre primer + tar topcoat	Inspect annually

Emergency Measures

When proper coating materials are not available, temporary measures:

• Any cooking oil or fat: Rub onto clean metal. Provides days to weeks of protection
• Soot/ash paste: Mix fireplace soot with fat. The carbon blocks oxygen. A crude but effective emergency barrier
• Wrapping in oily cloth: Wrap metal in a grease-soaked cloth for storage
• Keep dry: If you cannot coat metal, at minimum store it in the driest available location, elevated off the ground, with good air circulation
• Charcoal storage: Store metal items packed in dry charcoal — the charcoal absorbs moisture from the surrounding air

The most important principle: clean metal and coat it immediately. Delay is the enemy. Every hour of exposure to moist air is time lost to corrosion.