| MIC (MICROBIOLOGICALLY INDUCED CORROSION) |
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| This form of attack occasionally occurs under stagnant conditions in biologically active contaminated waters, often when hydrotest waters are left to stand in situ after testing. The above attack has occurred on Type 304 stainless steel plate material. |
Metal surface tree ring residue after removal of the tubercule. Pit in the center of rings, resultingin cavernous pitting attack in the wall of the plate, under the point of penetration. |
| AQUEOUS CORROSION |
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Aqueous corrosion can take many forms - pitting, crevice corrosion, general corrosion, galvanic attack. The above corrosion attack of a roller chain link belt, exposed to brackish water, resulted in the genegarl corrosion of Type 416 stainless steel rollers and end-grain attack of the pins.
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Type 416 stainless steel roller link belt allowed to sit in brackish water prior to commissioning of clarifier unit, resullting in general corrosion attack of the roller and chain, and end grain attack og the pin and bearing.
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| CORROSION |
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| Chlorination of brackish water with sodium hypochlorite pellets in a Type 316 stainless steel cyclone. Pellets sank and settled on sidewalls and bottom of tank, resulting in pitting attack by high concentrations of chlorine and chloride levels. Solution: Use calcium hypochlorite liqui to avoiod this problem and still attain chlorination. |
| MATERIAL SELECTION & SPECIFICATIONS |
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Archimedes lift pump screw in wastewater environment. Selection and specification of correct materials resulted in selection of Type 316 stainless steel. Alternate approaches included weld overlaying of original alloy steel units.
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| WELDING & WELD FABRICATION GUIDELINES |
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The need for cleanliness, weld preparation and weld clean-up are important components for making successful stainless steel welds. Eliminating heat tints is not only aesthetically desirable , but also ensures optimum corrosion resistance in aqueous service. |
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Establishing welding procedures for the field welding of Type 316 stainless steel sockets to pipe. In the pit making welded coupling-to-pipe joints between directionally drilled lengths of Type 316 stainless steel pipe. |
| CLEANING CONTAMINATED SURFACES |
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| The austenitic stainless steel do not rust, but iron contaminated surfaces do. Removal of these unsightly conditions can be undertaken with sound cleaning procedures, which may involve acid cleaning, mechanical removal or electropolishing. |
Before and after cleaning trial for the clean-up of iron-contaminated Type 304 stainless steel ducting to determine the appropriate acid cleaning procedure.
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