ChemistryMarichi · UPSC
Corrosion: Infrastructure ki Chupchaap Chunauti
Pul, pipeline, railway track aur ship ek hi dushman se ladte hain — corrosion. Kya ise 'maintenance ka mudda' maanein ya 'design aur policy ka mudda'?
Socho pehle… phir dekho jawab
Corrosion ek electrochemical prakriya hai: loha oxygen aur nami se jang mein badalta hai, aur namak (tatiya ilaake) ya acid rain jaise pradushan ise tez karte hain. Bachav material (galvanising, stainless steel, coating), design (paani na jame) aur cathodic protection se hota hai. GS3 mein ise infrastructure durability, life-cycle cost aur maintenance culture se jodo.
Concept: loha ki satah par anode (Fe → Fe²⁺ + 2e⁻) aur cathode (oxygen ka reduction) ki chhoti cells banti hain; paani ya namak electrolyte ka kaam karte hain. Isliye samudri ilaake aur pradooshit shehar zyada kharab hote hain. Jang bhurbhuri aur jhadne wali hoti hai, isliye woh andar ke loha ko bacha nahi paati; aluminium ka patla oxide, iske vipreet, andar ke dhaatu ko bacha leta hai.
Methods: (1) barrier coating — rang, tel; (2) galvanising — loha par zinc, jo sacrificial protection deta hai kyunki zinc zyada reactive hai; (3) alloying — stainless steel (loha + chromium, aksar nickel bhi); (4) cathodic protection — pipeline ya hull par zinc/magnesium ka sacrificial anode, ya impressed current jisme bahari DC se structure ko cathode banaya jaata hai; (5) design — paani ruk-ne wali jagah kam karna.
Prelims traps: (a) galvanising = zinc ki parat, tinning = tin ki parat. Tin loha se kam reactive hai, isliye parat khurach jaaye toh loha tezi se kharab hota hai; zinc ke saath aisa nahi. (b) Stainless steel ek alloy hai (loha + chromium), koi shuddh dhaatu nahi. (c) Jang self-protecting nahi hoti, jabki Al₂O₃ ki parat hoti hai.
Mains angle (GS3 infrastructure, S&T, environment): ek tark yeh hai ki sabse kam boli (lowest-bid) par kharidne ki aadat durability ko mehnga samajh kar nazarandaaz kar sakti hai; life-cycle costing, coastal zones mein sakht standard, aur maintenance budget ka sawaal isi se jude hain. Doosre paksh ka tark hai ki mehnge material ka kharch har jagah uchit nahi, isliye risk ke hisaab se chunna chahiye.
Ghar pe try karo
150 shabd likho: 'Infrastructure ki durability sirf engineering nahi, policy ka bhi sawaal hai — corrosion ke sandarbh mein.' Ek science ka point (anode-cathode ya sacrificial protection), ek udaharan (pul, pipeline ya jahaaz) aur ek policy suggestion (jaise life-cycle costing) shamil karo.
Wow!
Zinc ki ek patli parat apni 'qurbani' dekar loha bacha leti hai — aur pipeline par lagaye sacrificial anode isi siddhant se kaam karte hain!
3 sawaal
- Trap: sahi kathan chuno.
Jawab dekho
Galvanising mein loha par zinc ki parat chadhai jaati hai aur zinc sacrificial protection deta hai. Galvanising mein zinc zyada reactive hai, isliye woh pehle kharch hota hai. Tin loha se kam reactive hai; stainless steel alloy hai; jang self-protecting nahi hoti.
- Cathodic protection ke baare mein sahi kya hai?
Jawab dekho
Structure ko cathode banaya jaata hai, sacrificial anode ya impressed current se. Cathodic protection mein structure cathode banta hai; anode (zinc/magnesium) kharch hota hai ya bahari DC lagayi jaati hai.
- Stainless steel ki jang-rodhak kshamata kis kaaran hai?
Jawab dekho
Usme chromium hota hai jo patli oxide parat banata hai. Chromium ek patli, sakht oxide parat banata hai jo andar ke dhaatu ko bachati hai.
NCERT se jodo: GS3 — Infrastructure; Science & Technology (materials); Environment (acid rain, pradushan)