Research On Galvanic Corrosion And Protective Measures Of Shipbuilding Material

Galvanic corrosion that occurs on ship building materials in oceancircumstance has been investigated and analyzed comprehensively. According tonational standards. several types of representative ship building materials such as921.402.1Cr13.1 Cr18Ni9Ti and red copper were selected. and effects of many;factors such as regularity of these materia1s in 3.5% NaCl solution. condition ofaeration. area ration between cathode and anode on galvanic corrosion werestudied. Based on the result. concrete protective measures on how to lessen orprevent galvanic corrosion were proposed in this paper.The result of the studlt shows that: The corrosion behavior of high potentialdifference couple observes the theory of oxygen aggregation; but that of lowpotential difference couple does not observe it strictly. Its couple series becomesunstable. polarity inversion can happen during corrosion. When its surroundingis aerated with N2. the passive film of low potential difference couple behavesunstable and has low capability of self repairing, behavior of galvanic corrosionchanges little. When aerated with air. it shoxs obvious depolarization effect.corrosion is accelerated and electric contact effect is enhanced. In order todecrease or prevent the occurrence of galvanic corrosion. it was tbund outthrough experirnents that: Protection by coating is the most effective protectivemethods. it can not only improve the life span of anode but also provide dualprotection for cathode. because couple corrosion still exists as betbre. Protectionby sacrificial anode lower galvanic potential and thus can protect cathode of thecouple effectively: Protection by inhibitor is also feasible. but its application islimited, and as for anode. scanty amount of inhibitor can accelerate galvaniccorrosion.