Corrosion Background
Design Basis
Inner Surface
Outer Surface
Main Framework
As the main transportation equipment in the world, containers play an extremely important role in international cargo transportation. Ocean transportation is one of the main modes of container transportation. Ocean-going containers are used for a long time in the marine environment, especially those loaded on the deck of container ships, which are easily corroded by the marine atmospheric environment, thereby shortening the service life of the containers and increasing maintenance costs.
Based on the characteristics of the marine atmospheric environment, combined with the analysis of the principle of metal corrosion in the marine atmosphere, the use of coating anti-corrosion effects is applied to reduce the corrosion effect of the marine atmosphere on ocean-going transport containers, thereby achieving the goal of protecting container equipment and extending its service life.
Current national standards and regulations, mandatory standard provisions, etc;
《Code for Construction and Acceptance of Building Anti corrosion Engineering》 （GB50212-2002）
《Standard for corrosion grade and rust removal grade of steel surface before painting》 （GB8923-1988）
《Safety regulations and safety management rules for painting operations》 （GB6514-1995）
《Quality requirements for anti-corrosion coatings》 （GB6514-1991）
《Safety regulations for paint operations, paint process safety, and ventilation and purification》 （DJ/T6931-1999）
《Code for Construction and Acceptance of Industrial Equipment and Pipeline Anti corrosion Engineering》 （HGJ229-91）
《Safety regulations for painting operations - Safety of pre-treatment processes before painting》 （GB7692-87）
《Noise limits for construction site》 （GB12523-90）
ISO9001 Quality Management System Documents
ISO14001 Environmental Management System Document
GB/T28001 Occupational Health and Safety Management System Documents
Environmental conditions: The corrosion level of atmospheric environment on building steel structures under long-term action can be determined according to Table 1.
| Classification of Atmospheric Corrosivity and Typical Environmental Cases | ||||||
|---|---|---|---|---|---|---|
| Corrosivity level | Loss of mass and thickness per unit area（After the first year of exposure） | Typical environmental cases under warm climate conditions（For reference only） | ||||
| Bottom carbon steel | Zinc | Surface | Inner | |||
| Mass loss | Thickness loss | Mass loss | Thickness loss | |||
| /g·m2 | /um | /g·m2 | /um | |||
| C1 Low | ≤10 | ≤1.3 | ≤0.7 | ≤0.1 | / | Heated interior of buildings with clean air, such as offices, shops, schools, and hotels |
| C2 Low | ＞100-200 | ＞1.3-25 | ＞0.7-5 | ＞0.1-0.7 | Low pollution level atmosphere, mostly in rural areas | Unheated buildings where condensation may occur (such as warehouses, gyms, etc.) |
| C3 Medium | ＞200-300 | ＞25-50 | ＞5-15 | ＞0.7-2.1 | Urban and industrial atmospheres, moderate sulfur dioxide pollution, and low salinity coastal areas | In production plants with high temperatures and some air pollution, such as food processing plants, laundry plants, distilleries, dairy factories, etc |
| C4 High | ＞400-650 | ＞50-80 | ＞15-30 | ＞2.1-4.2 | Industrial and coastal areas with moderate salinity | Chemical plants, swimming pools, coastal ships, shipyards, etc |
| C5High | ＞650-1500 | ＞80-200 | ＞30-60 | ＞4.2-8.4 | Industrial areas with high humidity and severe weather, and coastal areas with high salinity | Buildings and areas where condensation and high pollution continue to occur and exist |
| CX Extreme | ＞1500-5500 | ＞200-700 | ＞60-180 | ＞8.4-25 | Marine areas with high salinity and tropical subtropical industrial areas with extremely high humidity and aggressive atmosphere | Industrial areas with extremely high humidity and corrosive atmosphere |
| Note: The loss value used to define the Corrosion level is the same as that given in ISO 9223. | ||||||
The salt spray content in the ocean atmosphere is relatively high, which has a strong corrosive effect on metals. From the perspective of corrosion, the marine atmospheric environment can be divided into five corrosion zones: the marine atmospheric zone, the wave splashing zone, the seawater tidal range zone, the seawater immersion zone, and the seabed soil zone. The area near the splash zone in the oceanic atmosphere has the greatest impact on metal corrosion, and ocean shipping containers are located in this area; Therefore, anti-corrosion protection for ocean shipping containers is particularly important.
The ocean atmosphere is rich in sea salt particles, forming an environment containing a large amount of salt gas, which is an important difference from other atmospheric environments. Salt particle impurities dissolve in the water film on the metal surface, turning the water film into a highly corrosive electrolyte and accelerating corrosion. Compared to the condensation film of clean atmosphere, air saturated with sea fog cycles can increase the corrosion rate of metals several times.
| Reference basis | The surface of metal materials exposed to the marine atmospheric environment is often in a state of alternating dry and wet changes, resulting in a high salt concentration on the metal surface, which affects the corrosion rate of metal materials | |||
|---|---|---|---|---|
| Corrosion environment | CX Extreme corrosion | |||
| Part | Indoor Environment | |||
| Service Life | 15-25 Year | |||
| Surface Treatment | Thoroughly spray rust removal to Sa2.5 level (ISO) 8501-1:2007), when observed without magnification, the surface should be free of visible oil, grease, and dirt, and there should be no oxide scale, rust, coating, or foreign impurities. Any residual traces of pollutants should only appear as slight color spots in the form of dots or stripes. | |||
| Painting area | Surface and interior of sea freight containers | |||
| Coating | Coating of coating | Paint name | ratio | Dry film |
| Step 1 | KnkaZinc | Graphene zinc foundation make-up KnkaZinc 60 Gns | 22.5：2.5 | 100μm |
| Step 2 | KnkaCover | Epoxy micaceous iron intermediate paint KnkaCover 150 | 22.5：2.5 | 160μm |
| Step 3 | KnkaDur | Hardtop AS KnkaDur 550 | 22.5：2.5 | 80μm |
| Actual total thickness | 340μm | |||
| Reference basis | The surface of metal materials exposed to the marine atmospheric environment is often in a state of alternating dry and wet changes, resulting in a high salt concentration on the metal surface, which affects the corrosion rate of metal materials | |||
|---|---|---|---|---|
| Corrosion environment | CX Extreme corrosion | |||
| part | Indoor Environment | |||
| service life | 15-25 Year | |||
| Surface Treatment | Thoroughly spray rust removal to Sa2.5 level (ISO) 8501-1:2007), when observed without magnification, the surface should be free of visible oil, grease, and dirt, and there should be no oxide scale, rust, coating, or foreign impurities. Any residual traces of pollutants should only appear as slight color spots in the form of dots or stripes. | |||
| Coating part | Surface and interior of sea freight containers | |||
| Coating | Type of coating | Coating name | Ratio | Dry film |
| Step 1 | KnkaCover | Graphene low surface treatment primer KnkaCover 220 Gns | 10：0 | 120μm |
| Step 2 | KnkaDur | Hardtop AS KnkaDur 550 | 10：0 | 80μm |
| Actual total thickness | 200μm | |||
The salt spray content in the ocean atmosphere is relatively high, which has a strong corrosive effect on metals. From the perspective of corrosion, the marine atmospheric environment can be divided into five corrosion zones: the marine atmospheric zone, the wave splashing zone, the seawater tidal range zone, the seawater immersion zone, and the seabed soil zone. The area near the splash zone in the oceanic atmosphere has the greatest impact on metal corrosion, and ocean shipping containers are located in this area; Therefore, anti-corrosion protection for ocean shipping containers is particularly important.
The relative humidity of the ocean atmosphere is relatively high, and the relative humidity of the air is higher than its critical value; Therefore, metal surfaces in the marine atmospheric environment are prone to forming corrosive water films. The thickness of the water film on the metal surface has a significant impact on its marine atmospheric corrosion, directly affecting the corrosion rate and mechanism of the metal. Compared with general atmospheric corrosion, the marine atmospheric environment has higher humidity, which can easily form a thicker water film on the metal surface. As the thickness of the water film increases, the corrosion rate accelerates. The experimental results indicate that if the relative humidity of the air is kept below 70%, the corrosion effect on metals is minimal; If the relative humidity of the air exceeds 70%, the corrosion rate of metals will accelerate.
| Reference basis | The surface of metal materials exposed to the marine atmospheric environment is often in a state of alternating dry and wet changes, resulting in a high salt concentration on the metal surface, which affects the corrosion rate of metal materials | |||
|---|---|---|---|---|
| Corrosion environment | CX Extreme corrosion | |||
| part | Outer wall of sea freight container | |||
| Service life | 25Year or more | |||
| Surface Treatment | Thoroughly spray rust removal to Sa2.5 level (ISO) 8501-1:2007), when observed without magnification, the surface should be free of visible oil, grease, and dirt, and there should be no oxide scale, rust, coating, or foreign impurities. Any residual traces of pollutants should only appear as slight color spots in the form of dots or stripes. | |||
| Coating part | Marine areas with high salinity | |||
| Coating | Type of coating | Coating name | Ratio | Dry film |
| Step 1 | KnkaZinc | Cold spray zinc KnkaZinc 96 | 10：0 | 80μm |
| Step2 | KnkaCover | Cold spray zinc sealing paint KnkaCover 167 | 10：0 | 160μm |
| Step 3 | KnkaDur | Hardtop AS KnkaDur 550 | 10：0 | 80μm |
| Actual total thickness | 320μm | |||
| Reference basis | The surface of metal materials exposed to the marine atmospheric environment is often in a state of alternating dry and wet changes, resulting in a high salt concentration on the metal surface, which affects the corrosion rate of metal materials | |||
|---|---|---|---|---|
| Corrosion environment | CX Extreme corrosion | |||
| part | Outer wall of sea freight container | |||
| Service life | 25Year or more | |||
| Surface Treatment | Thoroughly spray rust removal to Sa2.5 level (ISO) 8501-1:2007), when observed without magnification, the surface should be free of visible oil, grease, and dirt, and there should be no oxide scale, rust, coating, or foreign impurities. Any residual traces of pollutants should only appear as slight color spots in the form of dots or stripes. | |||
| Coating part | Marine areas with high salinity | |||
| Coating | Type of coating | Coating name | Ratio | Dry film |
| Step 1 | KnkaZinc | Graphene zinc foundation make-up KnkaZinc 60 Gns | 15：3 | 80μm |
| Step2 | KnkaCover | Epoxy micaceous iron intermediate paint KnkaCover 150 | 15：3 | 120μm |
| Step 3 | KnkaDur | Hardtop AS KnkaDur 550 | 15：3 | 80μm |
| Actual total thickness | 280μm | |||
From the perspective of corrosion, the marine atmospheric environment can be divided into five corrosion zones: the marine atmospheric zone, the wave splashing zone, the seawater tidal range zone, the seawater immersion zone, and the seabed soil zone. The area near the splash zone in the oceanic atmosphere has the greatest impact on metal corrosion, and ocean shipping containers are located in this area; Therefore, anti-corrosion protection for ocean shipping containers is particularly important.
The frequency of wet dry alternation on the surface of metal materials is influenced by various factors, including relative humidity of the air and sunlight duration. The former affects the frequency of wet dry alternation by influencing the thickness of the water film on the metal surface; If the latter is too long, it will accelerate the disappearance of the water film on the metal surface, shorten the wetting time of the surface, and thus reduce the total amount of corrosion.
| Reference basis | The surface of metal materials exposed to the marine atmospheric environment is often in a state of alternating dry and wet changes, resulting in a high salt concentration on the metal surface, which affects the corrosion rate of metal materials | |||
|---|---|---|---|---|
| Corrosion environment | CX Extreme corrosion | |||
| part | Main body of sea freight container | |||
| Service life | 25Year or more | |||
| Surface Treatment |
Thoroughly spray rust removal to Sa2.5 level (ISO)
8501-1:2007), when observed without magnification, the surface should be free of visible oil, grease, and dirt, and there should be no oxide scale, rust, coating, or foreign impurities. Any residual traces of pollutants should only appear as slight color spots in the form of dots or stripes. Thoroughly remove rust from manual and power tools to St2 level (ISO 8501-1:2007). When observed without magnification, the surface should be free of visible oil, grease, and dirt, and there should be no loosely attached oxide scales, rust, coatings, or foreign impurities. | |||
| Coating part | Marine areas with high salinity | |||
| Coating | Type of coating | Coating name | Ratio | Dry film |
| Step 1 | KnkaZinc | Cold spray zinc KnkaZinc 96 | 10：0 | 80μm |
| Step2 | KnkaCover | Cold spray zinc sealing paint KnkaCover 167 | 10：0 | 160μm |
| Step 3 | KnkaDur | Hardtop AS KnkaDur 550 | 10：0 | 80μm |
| Actual total thickness | 320μm | |||
| Reference basis | The surface of metal materials exposed to the marine atmospheric environment is often in a state of alternating dry and wet changes, resulting in a high salt concentration on the metal surface, which affects the corrosion rate of metal materials | |||
|---|---|---|---|---|
| Corrosion environment | CX Extreme corrosion | |||
| part | Main body of sea freight container | |||
| Service life | 25Year or more | |||
| Surface Treatment |
Thoroughly spray rust removal to Sa2.5 level (ISO)
8501-1:2007), when observed without magnification, the surface should be free of visible oil, grease, and dirt, and there should be no oxide scale, rust, coating, or foreign impurities. Any residual traces of pollutants should only appear as slight color spots in the form of dots or stripes. Thoroughly remove rust from manual and power tools to St2 level (ISO 8501-1:2007). When observed without magnification, the surface should be free of visible oil, grease, and dirt, and there should be no loosely attached oxide scales, rust, coatings, or foreign impurities. | |||
| Coating | Type of coating | Coating name | Ratio | Dry film |
| Step 1 | KnkaZinc | Cold spray zinc KnkaZinc 96 | 10：0 | 60μm |
| Step2 | KnkaCover | Cold spray zinc sealing paint KnkaCover 167 | 10：0 | 150μm |
| Step 3 | KnkaDur | Hardtop AS KnkaDur 550 | 10：0 | 50μm |
| Actual total thickness | 260μm | |||
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