What is the color inside a shipping container?
The color inside a shipping container is a special protective coating applied to the interior walls, ceiling and often also the doors of a standard transport container. Unlike the exterior coating, whose main function is protection from extreme weather and owner identification, the interior coating is optimized mainly for functionality, safety, easy inspection of cargo and protection against chemical and mechanical influences arising during transport and storage.
The standard is a light, neutral shade – most often light gray (RAL 7035), occasionally beige or off‑white. The reason is to maximize visibility in the dark interior of the container, facilitate visual inspection of goods, reveal pests, leaks, damage and increase safety when handling cargo. The condition and shade of the interior coating is an important indicator of the technical and aesthetic state of the container and its suitability for further use (transport, storage, conversions – e.g., to residential or office modules).
Detailed description and significance of the container’s interior coating
Functions of interior color:
| Function | Explanation |
|---|---|
| Protection against corrosion | Protects steel walls from moisture, chemicals and mechanical wear. |
| Visibility | Light shade increases illumination inside, eases handling and inspection of cargo. |
| Safety | Allows rapid detection of leaks, pests, mold, chemical residues or other defects. |
| Neutrality | Does not affect visual inspection of goods, does not discolor the cargo. |
| Psychological effect | A clean, bright interior looks professional and gives the customer a sense of safety and cleanliness. |
| Condition signalling | The condition and uniformity of the coating indicate the container’s history and preservation. |
Standard interior color and its strategic importance
Shipping container manufacturers worldwide follow an unwritten but widely recognized standard – the interior coating is always in shades of light gray, optionally beige. The most commonly used is RAL 7035(light gray). This shade has the highest light reflectance, which is crucial in a dark, enclosed space without natural light.
Advantages:
- Maximum visibility: Workers see better during loading and unloading, reducing the risk of injuries.
- Easier inspection: Customs and safety inspectors quickly identify contents, possible defects or illegal goods.
- Damage detection: Leaks, mold, penetrations are immediately noticeable.
- Neutrality: Light shades do not alter the colour of the transported goods.
Psychological aspect:
- A light, clean interior increases customer confidence and looks professional. In conversions to housing or offices it creates a sense of larger space and cleanliness.
Types and composition of interior coatings
The interior paint is not only an aesthetic layer – it forms a complex coating system that ensures long service life of the container and safety of the transported goods. The coating system usually contains several layers:
- Surface preparation:
- Steel walls and ceilings are shot‑blasted (sandblasted, water‑jet) to remove rust, oil and contaminants.
- The goal is an optimal roughness for perfect adhesion of the primer.
- Primer:
- Most often epoxy‑based with zinc phosphate or other anti‑corrosion additives.
- Protects metal from corrosion, acts as a barrier against moisture and chemicals.
- Examples: Rokoprim Container RK 103 (quick‑dry alkyd base), epoxy primers.
- Top coat:
- Most often epoxy or polyurethane paints, optionally modern high‑performance alkyd systems.
- Provide the final shade, ensure mechanical and chemical resistance, easy cleaning.
- Examples: Rokoemail S 2029 KO semi‑mat, Hostagrund 3‑in‑1, polyurethane 2‑in‑1 paints.
Typical properties of interior coatings:
- Fast drying: Allows quick production and maintenance.
- Thixotropy: Paint does not run, can be applied on irregular surfaces.
- High coverage: 10–12 m² /kg at a dry film thickness of 30–40 µm.
- Application: Spraying, roller or brush.
- Durability: High mechanical resistance to abrasion, moisture and industrial chemicals.
Dry film thickness (DFT):
- Normally 40–60 µm, up to 100 µm for some systems for increased protection.
| Coating system | Coating type | Application | Advantages and disadvantages |
|---|---|---|---|
| Two‑layer epoxy | Primer + top coat | New containers, repairs | Maximum durability, higher cost |
| Polyurethane 2‑in‑1 | Base + top in one | Fast renovations, conversions | Easy application, high durability, lower service life |
| Alkyd system | Primer + enamel | Cheaper systems, short‑term use | Fast drying, lower chemical resistance |
Influence of container condition on interior paint
| Container category | Interior paint condition | Typical signs |
|---|---|---|
| New / One‑trip | Nearly flawless, uniform, clean | Minimal wear, light shade |
| Used – Cargo Worthy | Worn, local repairs, scratches | Repairs in different shade, stains, cargo residues |
| Decommissioned – AS IS | Damaged, corroded, non‑uniform | Damage, rust, abrasion, odor |
Typical defects and repairs:
- Scratches, chips, repairs: Occur during handling with heavy equipment, pallets and goods. Repairs are often done with a darker anti‑corrosion paint.
- Contaminated floor: Plywood flooring is porous, absorbs odors and residues from previous cargoes.
- Corrosion: In older containers the paint may be completely broken, exposing rust.
- Chemical residues and mold: Found in poorly stored or decommissioned containers.
Exterior vs. interior paint: differences, purpose and specifics
| Property | Exterior paint | Interior paint |
|---|---|---|
| Purpose | Identification, weather protection, UV resistance | Visibility, cleanliness, inspection, corrosion protection |
| Typical shades | Brand‑specific (e.g., Maersk blue, Hapag‑Lloyd orange, anthracite RAL 7016) | Light gray RAL 7035, beige |
| Resistance | High UV and chemical resistance, polyurethane/epoxy | High mechanical and chemical resistance, easy cleaning |
| Service life | 10–15 years (climate and maintenance dependent) | 5–10 years (use, repairs and maintenance dependent) |
Health‑neutrality and certification specifics
For ordinary transport and storage of industrial goods, standard industrial coatings that do not release harmful substances after curing are sufficient. If a container is to be used for food, medicine, drinking water, or as living space, coatings with food‑grade certification or low‑VOC paints are recommended.
Basic recommendations:
- Ask the seller for a health‑neutrality certificate!
- For residential spaces: For shipping container homes prefer coatings certified to EN 71‑3 (toy safety) or with food‑contact certification.
- For food storage: Use epoxy or polyurethane coatings certified for food contact (requires special application and substrate preparation).
- Always ensure thorough surface preparation: Removal of existing layers, rust, and degreasing.
Practical experience and renovation recommendations
Recommended products:
- Hostagrund 3‑in‑1: Suitable for metal surfaces, also works on slightly corroded areas, easy application.
- Rokoemail S 2029 KO: Semi‑mat enamel based on alkyd resin, quick‑dry, suitable for interior and exterior use.
- Polyurethane 2‑in‑1 paints: Durable, quick‑dry, ideal for conversions to residential modules such as shipping container homes.
- Epoxy systems: Highest durability, requires multiple layers, suitable for extreme requirements.
Interior coating renovation procedure:
- Mechanically clean the surface (grinding, shot‑blasting).
- Degrease (technical gasoline, acetone).
- Repair larger damage and corrosion spots.
- Apply a primer (anti‑corrosion).
- After drying, apply 1–2 layers of top coat.
- Allow thorough curing according to the manufacturer’s recommendations.
Important:
- Apply paint in dry conditions and at temperatures above 10 °C.
- Observe recommended intervals between coats!
- Use protective equipment (gloves, respirator).
Contamination, odor and hygiene
A typical problem of older containers is odor emanating from the floor (plywood). The porous material absorbs smells from previous cargoes (rubber, chemicals, food, organic matter). Even a perfect interior wall coating will not guarantee trouble‑free use for food storage or habitation if the floor is not properly sealed or replaced.
Solutions:
- Thorough cleaning and drying of the floor.
- Treatment with a special sealing coating (epoxy, polyurethane).
- Use of odor absorbers (activated carbon, soda).
- Replacement of the floor with a new one (in extreme cases).
Related terms
| Term | Meaning |
|---|---|
| RAL | European colour standard (most commonly RAL 7035 for interior, RAL 7016 for exterior). |
| Corten steel | Special corrosion‑resistant steel used for container structures, still requires protective coating. |
| Cargo Worthy (CW) | Certification of structural and watertight suitability for international transport. |
| ISO certification | International standards for dimensions, strength and compatibility of containers. |
| CSC label | Official safety label on the container door, containing manufacturing data and inspection validity. |
Frequently asked questions (FAQ)
Is the interior colour the same for all containers?
No. New containers have a light gray, clean coating. Used containers may have scratches, repairs in different colours, contamination, rust.
Can I repaint the interior of a container myself?
Yes, it is common in conversions. Proper surface preparation (grinding, degreasing, rust removal) and a quality anti‑corrosion system are essential.
Is the interior coating health‑neutral?
Standard coatings are safe after curing. For food storage or habitation, choose coatings with food‑grade certification or low‑VOC products.
Why does a container smell even if the paint looks good?
The odor is mainly caused by the original plywood floor. The solution is to treat or replace the floor.
Does interior colour affect the temperature inside the container?
Only minimally. Temperature is mainly influenced by exterior colour and insulation.
Czech Republic, Třebíč 
WITHOUT SHIPPING 
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