大多數人認為不鏽（xiù）鋼是絕對不會生（shēng）鏽的，而生（shēng）鏽的就不是不鏽鋼了（le）。其實，一些含鎳低的不鏽鋼材質在一定的條件下也會生鏽的。不鏽（xiù）鋼方管具有抵抗大氣（qì）氧化的能力，同時也具（jù）有在含酸、堿、鹽的介質中耐腐蝕的能力。但其抗腐蝕能（néng）力的大小是隨其鋼質本（běn）身化學組成、加互狀態（tài）、使用（yòng）條件及環境介（jiè）質類型而改變的（de）。因此，不是任何一種不鏽鋼（gāng），在任何環境下（xià）都能耐腐蝕不生鏽。
Most people think that stainless steel will never rust, but stainless steel will not rust. In fact, some stainless steel materials with low nickel content will rust under certain conditions. Stainless steel square tube has the ability to resist atmospheric oxidation, but also has the ability to resist corrosion in medium containing acid, alkali and salt. However, the corrosion resistance of the steel varies with its chemical composition, additive state, service conditions and the type of environmental medium. Therefore, not any stainless steel, in any environment can resist corrosion and rust.
Square tube
不鏽鋼是靠其（qí）表麵形（xíng）成的一層極薄而（ér）堅固（gù）細密的穩定的富鉻氧化膜來防止氧原子滲入（rù）氧化，而獲得抗鏽蝕的能力。該薄膜如（rú）果遭到破壞，不鏽鋼方管就會失去（qù）抗鏽能力。日常中多見的破壞方式有如下四種：
Stainless steel is formed by a very thin, solid, compact and stable chromium-rich oxide film on its surface to prevent oxygen atoms from penetrating into oxidation, and to obtain the ability to resist corrosion. If the film is destroyed, the stainless steel square pipe will lose its rust resistance. There are four common ways of destruction in daily life:
（一）不鏽鋼方管表麵粘附有機物汁液（yè），在有水氧情況下，構（gòu）成有（yǒu）機酸，長時間則有機酸對（duì）金屬表麵的腐蝕。
(1) The surface of stainless steel square tubes is adhered with organic juice, which forms organic acids in the presence of water and oxygen, and corrodes the metal surface for a long time.
（二）在有汙染的空氣中，遇冷凝水（shuǐ），形成硫酸、硝酸、醋酸液點，引起化學腐蝕。
(2) In polluted air, when it encounters condensate water, it forms sulfuric acid, nitric acid and acetic acid liquid points, which cause chemical corrosion.
（三）不鏽（xiù）鋼方管表（biǎo）麵存積著含有其他（tā）金屬元素（sù）的（de）粉塵或異類金屬顆粒的附著（zhe）物，在潮濕（shī）的空氣中（zhōng），附著物與不鏽鋼間的冷凝水，將二者連成一個微電池，引發了電化學反應，保護膜（mó）受到破壞，稱之謂電（diàn）化學腐（fǔ）蝕。
(3) The surface of stainless steel square tubes contains dust containing other metal elements or adhesives of different metal particles. In humid air, the adhesives and the condensate water between the adhesives and stainless steel connect the two into a micro-battery, which causes electrochemical reaction and damages the protective film. It is called electrochemical corrosion.
（四）不鏽鋼（gāng）方管（guǎn）表麵粘附含有酸、堿、鹽類物質，引起局部腐蝕。
(4) The adherence of stainless steel square tubes to the surface contains acids, alkalis and salts, which causes local corrosion.
