OTHER COMMON EXAMPLES

Galvanic corrosion between steel plate and screw nut, and destructive corrosion on screw nut

Junction metal box for electricity circuit for lighting at external staircase

Explanation :

1. Galvanic corrosion occurs in contact area between galvanised cover plate and iron screw head because both of them exposes to outdoor rain and moist air and so the contact area is easy to be filled with water.
2. Destructive corrosion occurs on the iron screw head because it does not have any surface protection, such as painting, electroplating or galvanisation.

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Galvanic corrosion between metal fence and fixing bolts

Metal frame at railway station boundary

The fixing material is designed to be used outdoors and so has been hot dip galvanised. However, the steel bolt below required standard of galvanisation was used. As a result, moist air can penetrate into the bolt easily to take place corrosion.

Topic :

Prevention form galvanic corrosion

Fitting for doors

Using building components made of same materials, such as stainless steel hinge with fixing screw of same material, can ensure that there is no any galvanic corrosion. Although using stainless steel can provide no obvious corrosion and more durable, it is very expensive.

Prevention from galvanic corrosion

Metal frame fixtures

Using a high quality galvanised steel building component, such as angle frame, steel section and fixing bolts for structural work, can achieve free of corrosion. Moreover, galvanised steel is durable and has a reasonable cost.

Prevention from galvanic corrosion

Ventilation components at railway station

Using the way of paint baking on mild steel frame and filling silicon sealant to the gap between the mild steel and the stainless steel louvre, can make a double protection from corrosion within these two metals. This way can make sure that combination of different materials can be used to give a controllable cost.

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