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2500 |
SEM picture of a fracture surface of a corrosion scale. On the steel surface a porous topotactical magnetite layer and on the outer surface a epitactical layer of coarse magnetite octaeders have been formed. Caustic environment onder bopiler conditions. (foto KEMA, ref 61). |
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2501 |
Surface of a tube exposed under dry-out conditions and with sodiumphosphate water conditioning. The dryout area in this test tube is sharply bordered..(foto KEMA, ref 61).. |
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2502 |
The locations a, b, c and d in the tube in case nr 2501 where cross sections have been made for examination of the type of the oxide layers. (foto KEMA, ref 61). |
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2503 |
Oxide layers on the locations a, b, c and d of tube mentioned in case 2502. The oxide layer is thicker going into the direction of the dry-out. At location d (behind the dryout) the oxide is porous without real protection. (foto KEMA, ref 61). |
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2504 |
Corrosion scale in alkaline (NaOH) boiler water under heat flux conditions. In the scale a compact layer on the metal, porous part and coarse magnetite crystals. In the crust small boiling tunnels partly filled with the coarse magnetite crystals. (foto KEMA, ref 61). |
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2505 |
A typical corrosion scale in alkaline (NaOH) boiler water under heat flux conditions. In the scale a compact layer on the metal, porous part and coarse magnetite crystals. In the crust boiling tunnels are noticed due to the heat flux (foto KEMA, ref 61). |
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2506 |
Typical corrosion scale under heat flux corrosion in alkaline water. Phenomena of columnar boiling were noticed in the porous corrosion crust. The adherent layer detached over the whole area where the pits (from columnar boiling in alkaline water) were present. (foto KEMA, ref 61). |
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2511 |
Cross section of test tub tested in caustic water under dry-out conditions. After 3 days exposure the experiment was finished because we suspected that the corrosion was very fast. |
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2512 |
Even without the microscope the porous and coarse crystalline magnetit was visible very well. |
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2513 |
Undulating oxide on the outside of the layer. Magnetite crystals grow to each other, so resulting in compressive stresses and the undulating. |
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2514 |
Detail of the caustic corrosion scale. |
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2708 |
Results of steam blanketing laboratory tests on C-steel in sodium phosphate solutions with different Na/PO4 ratio's. Below Na/PO4=2.6 corrosion occurs because of the acid forming. In between 2.6 and 2.8 the samples did not corrode and deposits are formed. Above 2.8 alkaline corrosion occured. (foto KEMA, ref 61). |
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2800 |
Coordinated Phosphate Treatment (Following the Na3PO4) and Congruent Phosphate Treatment (following the Na2.6H0.4PO4 line). (ref 64). |
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2801 |
The Equilibrium Phosphate Treatment according to Stodoal (ref 64). |
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2820 |
On nucleate boiling locations in a evaporator tube pitting and intergranular corrosion took place. Carbonate has been found on the dark places in the cross section. From these pits carbonate Stress Corrosion Cracking was found too. (foto KEMA). |
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