lots of corrosion questions (long but easy points)?
ok, in chemistry class we have a new teacher for the next few weeks and she teaches really differently. i’ve been flat chat doing homework for all my other subjects and i really dont have time to try and re-learn what she is trying to teach us. could you please help me with several questions i need answered ASAP, i understand corrosion but not so much the differences in materials etc. so for the questions could you also make reference to WHY, ie their positions on the electrochemical series. thank you so much.
-why is it undesirable to coat screws with tin as a mean of protection?
-cadmium is often used to coat screws, why?
- a yacht made of copper alloy sheets fastened with steel screws begins to leak after only a few weeks in the water, why?
-given a choice of an off road vehicle having either a chrome plated steel bumper or a galvanised steel bumper, explain which one you would choose and why?
-explain why it is not necessary to apply a protective coating fo aluminium sheeting used for roofing?
-aluminium is suitable for manufacturing small dinghies but not for large ships, why?
-steel anchors that have been left on the sea bed for decades show little or no evidence of corrosion, why?
sorry its so much, but im snowed under with work just now and i’ll get around to learning it as soon as i can. stupid new teacher. =/
thanks babes xx
Hi . Several answers for you:
We never join two different metals because they create a galvanic cell in the presence of water, so the net result is one of the metals is corroded.
Aluminum is covered with a thin layer or aluminum oxide that doesn’t penetrate within the material more than a few mm. So, no paint required. Paint costs money and adds to the weight of the project.
Aluminum is used for larger ships, especially military ships – advantage – non-magnetic (not affected by magnetic mines). In general, aluminum is difficult to weld, so maybe, the answer to your question, smaller boats use aluminum structure joined together by rivets (quite labor intensive compared to welding).
Hope this helps.
Hi . Several answers for you:
We never join two different metals because they create a galvanic cell in the presence of water, so the net result is one of the metals is corroded.
Aluminum is covered with a thin layer or aluminum oxide that doesn’t penetrate within the material more than a few mm. So, no paint required. Paint costs money and adds to the weight of the project.
Aluminum is used for larger ships, especially military ships – advantage – non-magnetic (not affected by magnetic mines). In general, aluminum is difficult to weld, so maybe, the answer to your question, smaller boats use aluminum structure joined together by rivets (quite labor intensive compared to welding).
Hope this helps.
References :