Technical Data & Downloads
Technical Data
Salt Spray Hours
Salt spray testing, also known as salt fog testing or salt spray corrosion testing, is a widely used method for evaluating the corrosion resistance of applied materials and coatings
| PASSIVATION OVER 10 µm ZINC | HOURS BEFORE WHITE RUST | HOURS BEFORE RED RUST |
| Hexavalent Blue | 24-28 | 100-200 |
| Hexavalent Yellow | 96-175 | 250-500 |
| Hexavalent Green / Olive Drab | 150-225 | 400-750 |
| Hexavalent Black | 72-96 | 250-270 |
| TRI-valent EnviroPassTM | 200-400 | 500-750 |
| MegaZinc® | 400-600 | 500-900 |
| MegaZinc® Black | 250 | 300-500 |
Note:
This is on an average micron thickness of 10um, in a neutral salt spray test to less than 5%
MegaZinc® has 3 different Classes.
Environmental Corrosion Rates
Measuring environmental corrosion rates is crucial for assessing the durability and reliability of metallic materials for specific applications
Spec: ISO 9223
| CORROSION CLASS | CATAGORY | ENVIRONMENT (INTERIOR) | ENVIRONMENT (EXTERIOR) | CORROSION (ZINC) | GUIDE DURABILITY OF CHROMATE |
| = | = | = | = | (Average) | (MIN-MAX) |
| 0 | None | 0 | (0-0)um/YEAR | ||
| C1 | insignificant – Very Low | Heated buildings with clean atmospheres, such as offices, shops, schools, and hotels | = | 0.5 | (0-1)um/YEAR |
| C2 | Low | Unheated buildings where condensation can occur, such as depots, and sports halls. | Atmosphere with low level of pollution: mostly rural areas | 1.5 | (1-2)um/YEAR |
| C3 | Medium | Production rooms with high humidity and some air pollution; such as food processing plants, laundries, breweries | Urban and industrial atmosphere, moderate sulfur dioxide pollution; coastal areas with low salinity | 3 | (2-5)um/YEAR |
| C4 | High | Chemical plants, swimming pools, coastal ships, and boatyards. | Industrial areas and coastal areas with moderate salinity | = | = |
| C5 | V. High | Buildings or areas with almost permanent condensation with high pollution | Industrial areas with high humidity and aggressive atmosphere and coastal areas with high salinity | = | = |
| CX | Extremely High | Industrial areas with extreme humidity and aggressive atmosphere | Offshore areas with high salinity industrial areas with extreme humidity and aggressive atmosphere and subtropical and tropical atmospheres | = | = |
Understanding environmental corrosion rates helps engineers and materials scientists select appropriate materials, coatings, and corrosion protection strategies to mitigate degradation and ensure the long-term performance of structures, equipment, and components exposed to challenging environmental conditions
ROHS: Max Allowed PPM
| Component | Symbol | Max PPM |
| Lead | Pb | 1000 |
| Mercury | Hg | 1000 |
| Hexavalent Chromium | Cr | 1000 |
| Polybrominated Diphenylethers | PBB | 1000 |
| Decabromodiphenyl Ethers | DECA-BDE | 1000 |
| Cadmium | Cd | 100 |
ROHS, which stands for Restriction of Hazardous Substances, sets limits on the maximum concentration of certain hazardous substances in electrical and electronic equipment.
The maximum concentration is usually measured in parts per million (PPM). For example, under the ROHS directive, certain hazardous substances such as lead (Pb), mercury (Hg), cadmium (Cd), hexavalent chromium (Cr6+), polybrominated biphenyls (PBB), and polybrominated diphenyl ethers (PBDE) must not exceed specified maximum concentrations, typically measured in PPM, in electronic products placed on the market within the European Union (EU).
Typical Rust timeline
| Description of Stage | Typical Visual Signs | Approximate Time-frame* | Environmental/accelerating factors |
| Bare ferrous metal (iron or steel) newly exposed or stripped of coating. No major corrosion products yet. | Clean steel surface, possibly light surface oxidation film but no visible rust. | Hours to days | High humidity, salt spray, pollutants, condensation will speed next stage. |
| If zinc-coated (electroplated or galvanised), zinc reacts with O₂ and CO₂ to form a stable zinc-carbonate/hydroxide patina (especially with wet/dry cycles). (American Galvanizers Association) | Zinc coating remains intact; surface may dull to a matte grey as patina forms. | Weeks to months (e.g., 1-12 months) depending on environment and coating thickness | Frequent wet/dry cycles (good), ventilation, clean environment help proper patina formation. Trapped moisture, poor ventilation hamper it. |
| On zinc-coated parts stored or exposed to moisture/poor ventilation, a white‐powdery deposit forms (zinc oxide/hydroxide/carbonate) rather than a dense protective film. (Conklin Metal) | Whitish, chalky, waxy deposit on coated parts (especially in overlapping/stacked areas) | Days to weeks under adverse conditions | High humidity, standing water or droplets trapped between parts, lack of airflow/CO₂, chlorides or pollutants accelerate it. (American Galvanizers Association) |
| The zinc layer has been consumed or compromised (via white rust, mechanical damage, scratches), base ferrous metal is exposed. | Bare steel exposure, small rust spots beginning. | Months to years depending on coating thickness & environment | Salt spray, industrial atmosphere, acid/alkali exposure, mechanical damage, micro-galvanic effects. |
| Iron reacts with water + oxygen to form iron (hydr)oxides (ferric oxide etc.). The familiar red/brown rust that eats into steel. (Engineering-Edge) | Reddish-brown flaky rust, loss of material, pitting, surface roughness. | Months to many years (depending on environment & coating thickness) | Marine atmosphere, high salt content (chlorides), high humidity, acid rain, lack of maintenance all accelerate. |
| Extensive red rust, loss of section thickness, possible failure of part. | Large rust flakes, holes, severe pitting, possible structural failure. | Years to decades depending on severity | Severe exposures, cyclic loading, neglected maintenance, combined chemical attack (e.g., chlorides + acid) lead to this fastest. |
How White Rust Forms vs How Red Rust Forms
White rust:
- Occurs primarily on zinc‐coated surfaces (galvanised or zinc-plated) when the normal protective zinc patina cannot form properly because of lack of airflow, trapped moisture, and/or insufficient CO₂ access.
- The white deposit is a porous/gelatinous mixture of zinc hydroxides, oxides and carbonates that does not provide a dense protective barrier the way a proper patina does.
- Because the coating is compromised, the zinc layer may be consumed quickly, eventually exposing the steel substrate.
- Prevention: Ensure good ventilation, avoid stacking/trapping moisture, apply passivation and top-coats.
Red rust:
Accelerated by salt (chlorides), acid/alkali environments, high humidity, and mechanical damage to coatings.
Occurs on iron or steel when the protective barrier (zinc coating or paint) is breached and the steel is exposed to moisture and oxygen.
The iron oxidises to iron (III) oxides (ferric oxide etc).
Red rust is destructive — it actually corrodes the base metal, leading to section loss and structural issues.
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