自動車排気ガス凝縮水環境におけるマフラー用材料の耐食性評価

抄録

The inside corrosion of automotive mufflers collected in North America way investigated. Aluminized steel corroded severely by automotive exhaust gas condensates. The morphology of the corrosion of aluminized steel was a pit with a diameter of a couple of millimeters and Al coating remained around the pit. This pit-shaped corrosion is characteristic of the inside corrosion of aluminized steel and causes large corrosion depth. Low-Cr steels (type 409: 11%Cr-0.2%Ti, type 410L: 13%Cr-0.01%C) sustained a large number of pits, while high-Cr stainless steel (type 430J1L: 19%Cr-0.5%Cu-0.5%Nb) corroded slightly. The corrosion resistance of these materials was studied with a newly developed condensate corrosion test method which simulates the inside corrosion of automotive mufflers, especially the pit-shaped corrosion of aluminized steel. The life of the materials was estimated by extreme value analysis of the maximum corrosion depth obtained by the new test. The life of type 409 steel was 3.3 times as long as that of aluminized steel and the life of type 436 stainless steel (18%Cr-1%Mo-0.3%Ti) was 1.7 times as long as that of type 409 steel.