问题 问答题 简答题

地下管道的腐蚀机理是什么?

答案

参考答案:

地下管道的腐蚀机理是:电化学腐蚀。

金属管道与电解质接触时,由于金属表面的不均匀,如金属种类、组织、晶格方向、内应力、表面处理状况的差异,或者由于金属不同部位接触电解液的种类:浓度、温度、移动速度的差别,从而在金属表面出现阳极区和阴极区,阳极和阴极通过金属本身闭合而形成腐蚀电池,阳极区金属受到腐蚀;

另一种是由于杂散电流和管道与土壤形成电解池,杂散电流流出金属处为阳极,金属被氧化而遭腐蚀。

阅读理解

阅读下列短文,从每个小题所给的选项中选出最佳答案。

      I was in line waiting to pay. In line there were two people before me. A little boy was buying

some rather strange clothes. He chatted with anyone who was interested in the clothes and soon

we learnt that he was going to a kindergarten (幼儿园) party. He had done a great job of putting

together interesting costumes.

     I noticed that the little boy was paying mostly with change (零钱). It seemed that he had robbed

his pig bank (猪形储蓄罐) to do this shopping. However, the cashier told him he was short after

counting all the money. The boy thought for a moment and said, "Please keep the shirt and I will

come back with more money. "

     It was clear that he had already used all the money he had and he was $ 8. 00 short. The lady

in front of me said, "Well, I could pay half of that. "I told the boy that I could pay the other half.

We dug into our handbags. However, both of us only had ten-dollar bills (纸币) and we needed the

cashier to get the change for us. Other shoppers began digging into their pockets to find some change.

It was amazing and touching as all these strangers seemed to react (反应) with the same mind.

All wanted to be of help. Within minutes the cashier said, "I have too much money." The cashier

didn't need our ten-dollar bills. Then the lady in front of me, who had been the first to offer help,

said, "Wait! I didn't even get a chance to give anything!"

     I smiled at her and said, "You did your share, because it was your idea and you started all this."

The little boy smiled and thanked us. We wished him the best and he left. Ileft with a good feeling.

I had seen the love and goodness of others all around me. The woman in front of me smiled and said,

"It sure feels good to give, doesn't it?" I smiled back and said, "Yes!"

1. What is this passage mainly about?[ ]

A. Love and goodness.

B. Culture and tradition.

C. Friendship and honesty.

D. Communication and understanding.

2. Why did the writer and the woman both feel glad? [ ]

A. Because the boy had saved some money.

B. Because they both didn't need to give anything.

C. Because the cashier didn't look down on the boy.

D. Because all the shoppers around were willing to help the boy.

3. What does the underlined word" touching" most probably mean? [ ]

A. 令人感动的

B. 令人难过的

C. 令人失望的

D. 令人害怕的

4.What's the correct order of the following events?

a. The cashier got enough money for the boy's shirt.

b. The cashier counted the boy's money.

c. The shoppers looked for some change in their pockets.

d. The boy went to the line to pay.

A. b, a, c, d

B. b, c, a, d

C. d, b, c, a

D. d, c, a, b

选择题