Corrosion Prevent at Ion Technology

Corrosion prevention technology General Technical Requirements


CORROSION PREVENTION TECHNOLOGY


Contents

1 ............................................................................................. General guidelines 3 2 Specification of the environment categories appertaining to the corrosion stresses ................................................................................................................ 3

2.1 Categories for ground and water .................................................................... 3

2.2 Atmosphere corrosion categories .................................................................... 3

3Selection of coating systems suitable for corrosion categories according to EN ISO 12944-5 : 2000.....................................................................................44 Implementing of surface protection ............................................................. 4

4.1 Mechanical preparation, acceptance of metalwork ...................................... 4

4.2 Preparation of the surface according to EN ISO 12944-4 : 2000 ................ 5

4.2.1 Removal of sticking contaminations.....................................................54.2.2 Removal of originating contaminations...............................................5

4.3 Data of coating materials..................................................................................6

4.4 Completion of painting work according to guidelines of EN ISO 12944-7:

2000 ...................................................................................................................... 8

4.4.1 General specifications..............................................................................84.4.2 Execution...................................................................................................84.4.3 Inspection of the painting work.............................................................95 Paint coat system specification form, container inside. New task ........... 9 6 Paint coat system specification form, container outside. New task ....... 11

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CategoryCorrosion rate

^.m/year (unprotected carbon steel)

Typical environment example in temperate zone

External Internal

C4 50 to 80 Industrial and coastal areas with salt content.

Chemical plants, swimming pools.

1 General guidelinesSteel structures in the atmosphere, in the water and in the ground without any protection are exposed to corrosion resulting in damages. Therefore steel structures are usually protected to avoid corrosion damages, that the structures are resistant in their whole lifetime against corrosion effects occurring.The EN ISO 12944 standard series deal with the protection of structures of 3 mm minimum thickness made from unalloyed, or slightly alloyed steel by means of paint coat systems, or coatings, with all its characteristics, which are important to achieve a suitable protection.When selecting the external and internal coating system of the containers it has been a fundamental consideration to provide the suitable protection against different stresses by a minimal number of coating systems.

Essentially two kinds of corrosion stresses are discerned for the containers:

- The internal surface of containers for water storage.

- The external surface of containers being in contact with the air.

2 Specification of the environment categories appertaining to the corrosion stresses

2.1 Categories for ground and waterThe standard EN ISO 12944-2 : 2000 specifies the categories listed in Table 1. for structures submerged in water and laid in the ground.

Table 1

We have selected the stricter category Im2 to specify the internal coating system of the containers, since chemicals are fed into the containers both for water treatment and maintenance, thus its content can not be considered as sweet water.

2.2 Atmosphere corrosion categoriesThe EN ISO 12944-2 : 2000 standard classifies the atmosphere environment in six corrosion categories, which are, as follows:

C1 very lowC2 lowC3 medium

C4 high

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Category Environment Example

Im1 Sweet water River plants, water power plants.

Im2 Sea, or mixed water Structures of harbor areas, sluice gates, piers, coastal structures.

Im3 Ground Underground containers, steel pipelines.

C5-I very high (industrial)C5-M very high (sea)

We have selected the properly strict category C4 to specify the coating system of the external surface of the containers (being in contact with the air), also considering the arrangement and operation conditions of the containers.

Table 2

3 Selection of coating systems suitable for corrosion categoriesaccording to EN ISO 12944-5 : 2000

The following coating system types are suitable for protection of internal surfaces of containers submerged in water:

- epoxy primer, epoxy intermediate layer, polyurethane cover,

- epoxy primer, 2 layers of solvent free epoxy resin,

- 3 layers of solvent free epoxy resin.

We have selected from the above types the two-component, solvent free, epoxy resinbase coating material SIKACOR EG of 3 layers (see Chapter 5).For the protection of the external surface of the containers we have selected from thecoating systems suitable for the corrosion category C4. The coating system consisting ofthe epoxy primer containing corrosion preventing pigments, the intermediate layer withepoxy resin cement and the cover containing polyurethane cement.

The specified coating system (see Chapter 6):

- SIKACOR EG-phosphate

- SIKACOR EG 1-Rapid intermediate layer with iron mica

- SIKACOR EG 5 cover varnish colour („K)Of course, coating systems set up on the basis of similar cement material base from other manufacturers can be used in addition to the selected coating system; however their application references must be examined.

4 Implementing of surface protection

4.1 Mechanical preparation, acceptance of metalworkAfter completion of welding, but prior to filling up with water the weld seams must be arch grinded off, in order to avoid sharp corners, weld knobs and filler rod ends. The methods of improper and proper finishing are shown in Figure 1.

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Figure 1: Improper and proper finishing of weld seams

The metal pearls stuck to the surface when welding must also be removed, since protruding out from the surface, the effective coating thickness is reduced resulting in premature deterioration of the coating system.

4.2 Preparation of the surface according to EN ISO 12944-4 : 2000Object: Removal of sticking (grease, oil, preserver) and originating (rust, scale) contaminations from the surface prior to painting.

4.2.1 Removal of sticking contaminationsThe oil, grease, preservers, salts and similar contaminations must be removed with an appropriate method prior to further surface preparation. The methods are:

- Emulsion degreasing, rinsing with clear water, drying by blow off.- High-pressure water jet cleaning with a suitable detergent, then rinsing with clear water, drying by blow off.- Wiping off be means of a cloth saturated with organic solvent. The cloth must often be exchanged.

After completion of drying off the internal surface the solidity of welds must be inspected and the possible corrections be carried out prior to grit blasting.

4.2.2 Removal of originating contaminationsThe object is, to remove the rust, the rolling scale from the surface and to roughen the surface to ensure an adequate sticking of the coating system to be created. The method: The surface must be cleaned by means of compressed air dry grit blasting to achieve a cleanliness and roughness rate required for the primer.The dust is removed from the surface by compressed air. The returning fine dust is removed by means of a brush vacuum cleaner and the surface cleanliness should be inspected.The surface must be wiped off with solvent prior to painting.The ordinary standard preparation rates of the grit blasting process and the features of the prepared surface are shown in Table 3.

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Rate Features of the prepared surface

Sa 2 Most part of scale, rust, paint coating and foreign materials is removed. Any remaining contaminations must firmly stick.

Sa 2 y2 The scale, rust, paint coating and foreign materials are removed. Any remaining contamination traces occur only as small stains, dots, or stripes.

Sa 3 The scale, rust, paint coating and foreign materials are removed. The surface has a uniform metallic color.

Table 3

The roughness of the internal surface of the container submerged in water is determinedby measuring, or according to the standard EN ISO 8503.

The cleanliness of the surfaces is appraised according to EN ISO 8502-3 : 1992.

4.3 Data of coating materialsTechnical data of application of the selected coating materials are shown in Tables 4 to 7.

Coating material Epoxy resin base, solvent free, two-component paint SIKACOR EG Phosphate

Color RAL 1014 ivory and ginger brown

Cement Solvent free epoxy resin - polyamine

Storage time 12 months in original packing

Surface preparation Blasting: cleanliness rate Sa

3 roughness > 50 pmMixing rate A : B = 100 : 35 mass ratio

Pot life at 20 °C 20 to 40 minutes depending on the quantity

Layer thickness 150 µm/layer (wet layer thickness 150 µm)

Number of layers 3

Drying at 20 °C Hand-dry: 2 hoursRe-paintable: 12 hours, max. 36 hours Loadable: 12 hours Stress: 7 days*

Applying Brush painting/rolling

Applying temperature Minimum + 10 °C.

* Because of temperature changing 14 days are safer.Table 4: Data of coating material selected for the internal surface of the container submerged in water

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Coating material Epoxy resin base, zinc phosphate, two- component primer SIKACOR EG Phosphate

Color RAL 8012 rusty brown

Cement Solvent epoxy resin - polyamine-amide adduct


Surface preparation Blasting: cleanliness rate Sa 2 ^ roughness normal

Mixing rate A : B = 5 : 1 mass ratioPot life at 20 °C 3 hours

Layer thickness 80 µm/layer (wet layer thickness 160 to 170 µm)

Number of layers 1 or 2 (if it can not be applied without running off)

Drying at 20 °C Hand-dry: 2 hours Re-paintable: 5 hours Loadable: 8 hours Stress: 4 days

Applying Brush painting/rolling Air spraying Airless spraying

Table 5: Data of primer selected for the external surface of the container

Coating material Epoxy resin base, iron mica, two-component coating material, SIKACOR EG 1

Color RAL 7032 grey

Cement Solvent epoxy resin - polyamine-amide adduct


Mixing rate A : B = 5 : 1 mass ratioPot life at 20 °C 3 hours

Layer thickness 80 µm/layer (wet layer thickness 150µm)

Number of layers 1 or 2 (if it can not be applied without running off)

Drying at 20 °C Hand-dry: 2 hours Re-paintable: 5 hours Loadable: 8 hours

Stress: 4 days

Applying Brush painting/rolling Air spraying Airless spraying

Table 6: Data of the intermediate layer selected for the external surface of the container

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Coating material Polyester base, two-component, polyurethane cover varnish color SIKAKOR EG 5

Color RAL 5019 blue

Mixing rate A : B = 5 : 1 mass ratio (with 2K fast hardener)

Pot life at 20 °C 6 hours

Layer thickness 35 µm/layer (wet layer thickness 70µm)

Number of layers 1 or 2 (if it can not be applied without running off) In case of applying of several layers drying between the layers should be ensured)

Drying at 20 °C Hand-dry: 4 to 6 hours Dry: 24 to 30 hours Stress: 4 days

Applying Brush painting/rolling (only with 2K fast hardener) Air

spraying Airless spraying

Thinning for rolling KH - 140 thinner, 0 to 5 % + 2 % brush additive

Table 7: Data of cover varnish color selected for the external surface of the container

4.4 Completion of painting work according to guidelines of EN ISO 12944-7 : 2000

4.4.1 General specificationsThe companies and their employees entering into the agreement for applying the paint coat system on the steel structure must be suitable for accurate and safe execution of the task.If the contractor has a functioning quality management system, a quality plan must becreated, including the general professional regulations and a statement concerning themethods must be made for each working stage.The EHS (environment, health and safety) regulations must be kept.The surface to be painted must be safely accessible and well illuminated.When using the coating materials the technical data sheet of the manufacturer must beconsidered.The applied processes depend on the type of the coating material, the surface, the shape and size of the structure and the local conditions, respectively.

4.4.2 ExecutionThe first primer layer is applied by brush painting on the external and internal surfaces. Special care is required when creating the coating in the corners, on the weld seams, on the brackets welded in for retaining the internal fittings and the frameworks fastened with bolted joints.The primer layer must cover the whole surface profile of the steel surface.

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Any faults occurring on the paint coat, that could result in a reduced protection capacity of the coating, or have a significant effect on the appearance must be repaired prior to applying the next layer.The next layers can be applied keeping the appropriate repainting and drying time by means of rolling, but special care is required when creating the coating in the corners, on the weld seams, on the brackets welded in for retaining the internal fittings and the frameworks fastened with bolted joints.When applying the wet coat material the creation of a uniform coat of the necessary thickness can be ensured by measuring the wet layer thickness, thus this must be required from the painters.

The specified thickness of each layer must be controlled after drying of the layer. 4.4.3

Inspection of the painting workThe execution must be inspected in every stage of working. The inspections must be carried out by accordingly qualified and skilled experts.Basically the contractor himself is responsible for the execution of the inspection, however it is also expedient for the customer to check, or have checked the corrosion prevention work.

After finishing the work the coating must be inspected with respect to the compliance.

1. Visual inspection, for example unevenness, color, covering, faults.

2. With instruments:- Dry layer thickness (with a destruction-free method). Unless any other agreement, no single values less than 80 % of the nominal dry layer thickness can be accepted. It is recommended at the same time, that the greatest dry layer thickness should not exceed three times the nominal layer thickness.- Adhering (destruction method, then to be repaired); Acceptance: > 2 MPa.

5 Paint coat system specification form, container inside. New task.

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APPLYING IN THE WORKSHOP

RATE OF SURFACE PREPARATION: Sa 3, Rz > 50 µm

TYPE OF WORKSHOP PRIMER (if any):

Paint manufacturer: Area: m2

PAINT COAT SYSTEM Nominal dry Repainting interval Drying time

layer Minimum Maximum at 20 °Cthickness hours hours hours

µmLayer 1: SIKAKOR EG phosphate

120* 12 36 8

Layer 2: SIKAKOR EG 1 120* 12 36 8

Layer 3: SIKAKOR EG 5 120* 12 36 8

IN ALL 360

NOTE: * Several working processes may be necessary.

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6 Paint coat system specification form, container outside. New task.

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APPLYING IN THE WORKSHOP

RATE OF SURFACE PREPARATION: Sa 2 %

TYPE OF WORKSHOP PRIMER (if any):

Paint manufacturer: Area: m2

PAINT COAT SYSTEM Nominal dry Repainting interval Drying time

layer Minimum Maximum at 20 °Cthickness hours hours hours

µmLayer 1: SIKAKOR EG phosphate

80* 5 8

Layer 2: SIKAKOR EG 1 80* 5 8

Layer 3: SIKAKOR EG 5 40* 24 24 to 30

IN ALL 200

NOTE: * Several working processes may be necessary.

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Corrosion Prevent at Ion Technology

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