corrosion of stainless steel - Damstahl

More documents

Recommendations

Info

Stainless Steel and Corrosion 6 RS for alle.indb 6 9/29/2011 12:44:11 PM
CHAPTER 6 CORROSION OF STAINLESS STEEL Repassivation of chromium oxides Stainless steel is almost the perfect material for critical applications, but as with all other near-perfect materials stainless steel has its limitations. The steel cannot be subjected to just anything without consequence, and in the majority of cases the limitations of the steel are defined by its resistance to corrosion. Stainless steel is unfortunately not always as stainless as its impressive name suggests. Stainless steels usually excellent resistance to corrosion is down to an ultrathin layer of oxides of especially chromium and iron, and although this film is only a few nanometres thick, it is still so dense and strong that the steel is effectively 'isolated' from the surrounding environment - similarly to an ultrathin paint. If, despite all precautions, a hole occurs in the protective oxide layer, it quickly restores itself, and the steel is again protected. This mechanism is called repassivation. Unfortunately, even the best-laid plans can go awry. Under unfortunate circumstances, the oxide layer can break down without subsequently being restored, and this may result in serious corrosion attacks. Once the corrosion has commenced, penetration may occur rapidly, and the use of stainless steel therefore often becomes a kind of either/or situation where the difference in between the two extremes is very slight. If corrosion initiation can be prevented, stainless steel will last almost forever. If not, serious corrosion will occur very quickly, and the life of any equipment can become alarmingly short. Stainless steel is only conditionally stainless. Depending on the type of steel and environment, stainless steel can be attacked by a whole range of more or less damaging types of corrosion. General corrosion Intergranular corrosion Crevice corrosion Pitting corrosion Stress corrosion cracking Figure 6.1: Stainless steel is only ”conditionally stainless”, and, depending on steel quality and environment, there is a risk of a whole host of corrosion nightmares. Pitting corrosion and crevice corrosion are both quite common and are often collectively referred to as 'local corrosion'. 73 RS for alle.indb 73 9/29/2011 12:44:32 PM
Page 2 and 3: STAINLESS STEEL AND CORROSION by Cl
Page 4 and 5: FOREWORD For most people, stainless
Page 6 and 7: HERE YOU GO Some readers may sit wi
Page 8 and 9: Take good care of it! Stainless Ste
Page 10 and 11: 5. CORROSION IN GENERAL 51 5.1 What
Page 12 and 13: 9.2 Pipes and Tubes 175 9.2.1 HF-we
Page 14 and 15: 14. CHECKS 297 14.1 Checking the Ma
Page 16 and 17: Stainless Steel and Corrosion Globa
Page 18 and 19: Stainless Steel and Corrosion Figur
Page 22 and 23: Stainless Steel and Corrosion Gener
Page 24 and 25: Stainless Steel and Corrosion Tempe
Page 26 and 27: Stainless Steel and Corrosion Anodi
Page 28 and 29: Stainless Steel and Corrosion Auste
Page 30 and 31: Stainless Steel and Corrosion Figur
Page 32 and 33: Stainless Steel and Corrosion Passi
Page 34 and 35: Stainless Steel and Corrosion CPT [
Page 36 and 37: Stainless Steel and Corrosion CPT v
Page 38 and 39: Stainless Steel and Corrosion altho
Page 40 and 41: Stainless Steel and Corrosion 6.2.5
Page 42 and 43: Stainless Steel and Corrosion EN AI
Page 44 and 45: Stainless Steel and Corrosion Diffe
Page 46 and 47: Stainless Steel and Corrosion Nicke
Page 48 and 49: Stainless Steel and Corrosion 6.3 C
Page 50 and 51: Stainless Steel and Corrosion This
Page 52 and 53: Stainless Steel and Corrosion Poten
Page 54: Stainless Steel and Corrosion Addit

corrosion of stainless steel - Damstahl

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?