'CORRODERE' OF NON-METALLIC MATERIALSIN THE MINING, OIL GAS INDUSTRIES (MOGI)

摘要

Corrodere is the Latin term for gnawing or slow degradation, which can gradually lead tornthe loss of physical and/or mechanical properties in non-metals and cause problemsrnsuch as leaks. It often promotes serious corrosion of the metal substrate, and requiresrncostly repairs in the mining, gas and oil industries (MOGI). Polymers and chemicalsrnwhich are used for corrosion protection can themselves become a main feature ofrncorrodere. Coatings, liners, umbilicals, O-rings, seals or other protective systems can allrnbe attacked in a slow but insidious way.rnHydrolysis of the polymer is one of the most common breakdown mechanisms, whichrnapplies to polymers such as nylon, polyurethanes, and polyesters that havernhydrolysable linkages in the main chain. Other mechanisms include oxidativerndegradation, particularly if air can gain access, and biodegradation of the polymer.rnAccelerated aging tests followed by mechanical testing and molecular weight analysisrnare the most useful general methods for appraisal of the likely future state of thernpolymeric material.rnSome of the following examples of polymer compromised corrosion susceptiblernsituations will be discussed:rn· Replacement of metal shims and wedges with polyurethane elastomersrn·The chemical degradation of corrosion inhibitorsrn·An engineers nightmare: choosing the best Viton elastomer for the jobrn·The performance of Viton A seals in diesel engine coolantrn·Gnawed seals, extrusion, explosive decompression, and cold flowrn·Corrosion inhibitors and emulsion formation under severe conditionsrn· Acid resistant epoxies for pipe and tank coatingsrn· Microbacterial corrosionrn· Microbial degradation of epoxy coatings in a damp sulphur environmentrn· Amine blush of epoxiesrn· Entomological attack on plastics.