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Marine Corrosion Protection

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Corrosion Protection SEO Vianden Quality of Coating Products. Studies by the SEO Construction Department
of Selected Products.

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Marine Corrosion Protection

  1. 1. Corrosion Protection SEO Vianden Quality of Coating Products Studies by the SEO Construction Department of Selected Products
  2. 2. Introduction <ul><li>Purpose of the studies: </li></ul><ul><li>Determining the quality of the coating systems for difficult corrosion protection in hydraulic steel structures. </li></ul><ul><li>Comparison of various corrosion protection products . </li></ul><ul><li>Statements concerning the durability of the protective effect of the various corrosion protection products. </li></ul>
  3. 3. Main Topics <ul><li>Function of the coating materials </li></ul><ul><li>Properties of the coating materials </li></ul><ul><li>Test methods </li></ul><ul><li>Water diffusion test (description/results) </li></ul><ul><li>Findings </li></ul>
  4. 4. Function of the coating materials <ul><li>Coating materials are supposed to maintain a barrier function between steel (substrate) and water , which lasts as long as possible, in order to prevent corrosion damage. </li></ul><ul><li>For this purpose, they must be as watertight as possible . </li></ul>
  5. 5. Properties of the coating materials <ul><li>The polymer structure of the coating materials results in a greater or lesser porosity of the coating film. </li></ul><ul><li>This permits water to penetrate as a function of the type and quality of the binder, the pigments/fillers, and solvent content, etc. </li></ul><ul><li>Coatings can be regarded as a permeable membrane (more or less solid, cross-linked polymer film). </li></ul><ul><li>Diffusion depends on the structure and thickness of the covering layer . </li></ul>
  6. 6. Diffusion and its consequences Functional mechanism <ul><li>Corrosion residues and salts on the steel surface, which strive to become diluted, attract water through the coating (e.g. iron sulfate). </li></ul><ul><li>Salt solutions form on the steel surface and this results in a concentration gradient between the outside and the inside of the coating. </li></ul><ul><li>An osmotic pressure develops, which allows more and more water to flow through the coating in the direction of the substrate (steel). </li></ul><ul><li>Bubbles filled with water form on the coating, leading to the detachment of the coating and finally to its bursting. </li></ul><ul><li>This leads to local corrosion damage at first, later to large-area corrosion damage (pitting, rust, etc.) </li></ul>
  7. 7. Material transport through coatings Consequences for the coating <ul><li>Water absorption, caused by osmosis, depends on the binder and the pigmentation. </li></ul><ul><li>-> it brings about swelling of the coating  a decrease in cohesion and, </li></ul><ul><li>with that, a decrease in tensile strength perpendicular to the </li></ul><ul><li>surface (cohesion rupture) </li></ul><ul><li> -> it influences the chemical bonding of the coating to the substrate  </li></ul><ul><li>Decrease in adhesion  Bubbles or loosened areas occur. </li></ul>
  8. 8. Practical example : Ball valve pressure plate TU2, coated in 1999, partially stressed (with Sika Poxitar SW 200-250 µm), findings after eight years
  9. 9. Other factors can influence the diffusion process: <ul><li>Salt residues, dust, dirt on the substrate </li></ul><ul><li>Solvents in the coating </li></ul><ul><li>Water quality </li></ul><ul><li>Binder residues, which have not been cured </li></ul><ul><li>Primers, base coats </li></ul>
  10. 10. The following counteract the diffusion process: <ul><li>Diffusion resistance of the product </li></ul><ul><li>Layer thickness of the product </li></ul><ul><li>Adhesion strength of the coating </li></ul><ul><li>Cleanliness of the substrate surface </li></ul>
  11. 11. Test methods used for quality studies of substrate and coating material (at SEO) <ul><li>Substrate quality : - Visual comparison with standardized comparison </li></ul><ul><li>samples , </li></ul><ul><li> - Salt concentration studies , </li></ul><ul><li>- Examination for dust residues , </li></ul><ul><li>- Measurements of the roughness of the steel surface </li></ul><ul><li>Tensile Adhesive Adhesion testing equipment (tensile force perpendicular strength : to the die that is glued on) </li></ul><ul><li>Diffusion resistance : Δ -T Test </li></ul>
  12. 12. Diffusion resistance / Δ -T Test: Test arrangement (thermodiffusion)
  13. 13. Diffusion resistance /  -T Test Of central importance for corrosion protection <ul><li>Parameters determining the diffusion rate of water through the coating to be tested : </li></ul><ul><li>Temperature (Gradient,Difference) </li></ul><ul><li>Layer thickness </li></ul><ul><li>Quality of the coating </li></ul><ul><li>Application of the coating </li></ul><ul><li>Assessment criterion : </li></ul><ul><li>Diffusion period in days until bubbles appear on the coating surface </li></ul>
  14. 14. Criteria in similar tests by the main RWE Laboratory Studies for the selection of products for coating the pressure lines 1 and 2 of the PS power plant Vianden 1997/98) <ul><li>A coating should withstand the tube test for approximately 20 days (at 40/10°C) without forming bubbles, in order to be able to achieve a resistance of at least 20 years (experience of RWE laboratory). </li></ul>
  15. 15. Coating after diffusion of water (in the thermodiffusion test) Example: Tenaxon 555CS (version 2007, epoxy, solvent-based, average layer thickness 500 µm) Outside bath temperature 40°C/inside temperature in experimental tube 10°C Time period until the first bubbles appear: 2 days
  16. 16. Coating after diffusion of water in the thermodiffusion test (  -T Test) <ul><li>Example: </li></ul><ul><li>Caparol Disbon 705 </li></ul><ul><li>Polibrid coating </li></ul><ul><li>600 to 1500 µm </li></ul><ul><li>Time period until bubbles form </li></ul><ul><li>approximately 10 days in the </li></ul><ul><li>region of 700 µm </li></ul>
  17. 18. Comparison of test tube test / WDD test according to DIN EN ISO 6270 (Water vapor (40°C) applied to plate, back side: air (20-25°C), layer thickness 500 µm, bubbles form after approximately 1 year in the case of ICOSIT) SIKA ICOSIT 500 SW ACOTEC HUMIDUR ML
  18. 19. Diffusion period in days until the appearance of bubbles on the coated surface in relation to the layer thickness in µm (Selection from more than 40 different tests and products until now)
  19. 20. Conclusions from the Table: Durability of the corrosion protection <ul><li>Based on the results found in the diffusion test and the previous results from the RWE laboratory tests, there are only </li></ul><ul><li>a few coating materials that pass the test over a period of more than 17-20 days, at an average layer thickness of 500 µm, without forming bubbles: </li></ul><ul><li>HumidurML from 1999 at 400 µm 17 days (with 2 mm tube) </li></ul><ul><li>(More recent batches, however, show lower values in spite of repeated complaints  raw materials for the curing agent have been changed) </li></ul><ul><li>Aquapure HR : at 480 µm, more than 90 days without forming bubbles </li></ul><ul><li>Interzone 954 : at 350 µm 45 days (solvent-based) </li></ul><ul><li>CeramKote 54: at 500 µm more than 40 days without forming bubbles </li></ul><ul><li>Epiter 130 TF: at 400 µm 21 days (solvent-based) </li></ul><ul><li>These products will offer long-term corrosion protection if applied correctly. </li></ul>
  20. 21. Findings <ul><li>The coating will last longer if its diffusion resistance is higher. </li></ul><ul><li>Water is kept away from the substrate as long as possible. </li></ul><ul><li>Any contaminants that might be present will react more slowly. </li></ul>
  21. 22. Selection criteria for application in the various water power plant sectors: <ul><li>Long durability of the corrosion protection </li></ul><ul><li>Application method </li></ul><ul><li>Ease of repair </li></ul><ul><li>Environment and health </li></ul>
  22. 23. Application methods <ul><li>For application in accordance with good practice, the following criteria should be observed: </li></ul><ul><li>Application temperatures (substrate, coating, atmosphere) </li></ul><ul><li>Equipment (spraying, brush-coating) </li></ul><ul><li>Processing time (pot life) </li></ul><ul><li>- Ability to apply multiple coatings (multiple layers, repairs) </li></ul>
  23. 24. Environment and Health <ul><li>The products selected must not contain any materials that are harmful to the environment and to health : </li></ul><ul><li>(VOC guideline and REACH regulations) </li></ul><ul><li>no solvents </li></ul><ul><li>no polycyclic aromatic hydrocarbons </li></ul><ul><li>no carcinogenic materials </li></ul><ul><li>n components that contaminate water </li></ul>
  24. 25. Advantages and disadvantages of the aforementioned products in comparison with one another: no no no yes no Allowed for drinking water R11/20/36/37/38/43/21/22/34/37/51/53/66/67/ R10/11/20/21/22/34/36/37/38/43/51/52/53/66 R34/43/20/22/36/38/43//51/53 R21/22/23/24/25/34/36/38/39/43/45/48/51/52/53/68/ R45 carcinogenic R groups / >15 >20 >20 >20 Adhesion strength N/mm2 90-120 poor 125 µm 450 µm VOC 130g/l 45 ++ Interzone 954 4/1vol 45 good / 450 µm VOC 28g/l 21 ~0 EPITER TF 130 4/1weight very poor 125 µm 450µm VOC168g/l >40 ++ Ceram-Kote54 6.7/1weight >90 ++++ (for 300 µm 35days.) 20 ~ Diffusion resistance in days for 500-600 µm 30 very good 40 good Processing Pot life at 18°C in min Manual processing / 350 µm / 370 µm Max. layer thickness Min. layer thickness none none Solvent content Aquapure HR 1/1 Humidur ML 1999 5/1weight
  25. 26. Next Steps <ul><li>Detailed study of the Aquapure HR und Interzone 954 by the RWE </li></ul><ul><li>laboratory; comparison with HUMIDUR ML (1999/2007) </li></ul><ul><li>Further studies of other products </li></ul><ul><li>e.g. products that are being used by EDF in France </li></ul>