在不鏽鋼中存在的鉻是否包含六價鉻(Cr6+),是否對人體有潛在的危害?

原文地址：http://www.bssa.org.uk

原創翻譯：龍騰網 http://www.ltaaa.com 翻譯：hellokitty221

正文翻譯：

Does the chromium in stainless steel contain 'chrome 6' (Cr6+ ) and is this a potential health hazard

標題：在不鏽鋼中存在的鉻是否包含六價鉻(Cr6+)，是否對人體有潛在的危害？

Valency states of chromium

鉻的價態

The valency (oxidation state) of chromium metal as an alloying constituent of stainless steels is 0 (zero).

當鉻元素以不鏽鋼合金存在的時候，鉻的價態（即氧化狀態）是0(zero)。

Chromium atoms are present in stainless steels in 'substitutional' lattice positions, replacing iron atoms. This is the same as other 'large' atoms from elements such nickel. The atoms are held together in the lattice structure by the 'metallic bond'. This involves the sharing of electrons between atoms with no loss or gain of electrons from atom to atom. The valency state is therefore taken as 0 (zero).

鉻的原子是以一種「替代式的」晶格位置，代替鐵原子存在於不鏽鋼之中。這和不鏽鋼中的其它大量元素的原子的狀態一樣，比如鎳。這些個原子通過「金屬鍵」以晶格結構結合在一起。這使得原子之間的電子共享而原子相互間並沒有得到或者失去電子。這樣的價態被稱作為0(zero)。

The chromium in solid stainless steels should not be regarded as a health hazard.

因此，在固態不鏽鋼合金中的鉻不應被當作健康的危害因素。

In contrast ionic bonding in compounds, such as sodium chloride (common salt), involves the exchange of electrons between atoms and hence valency states of 1, 2, 3 etc depending on how many electrons the element has lost or gained. It is compounds involving chromium 'ions' with a valency state of 6 (which includes chromates) that have been identified as a cause for health concerns. This valency state is also referred to as 'chromium 6', 'hexavalent chromium' or 'Cr6+'

對比化合物中的離子鍵結合，比如氯化鈉（即鹽），它的原子間存在電子交換，它的元素得到或者失去了不同數量的電子因而產生了1，2，3等不同的價態。如果有種化合物使得鉻離子形成了6這個價態（其中包括鉻酸鹽）那麼這種化合物是對體有害的。這個價態也被稱為「6價鉻」、「六價鉻」或「Cr6+」。

Release of chromium if stainless steels corrodes 

不鏽鋼受到腐蝕時析出的鉻

If stainless steels are subject to corrosion metal ions are released from the alloy into the surrounding environment. Under these conditions, chromium ions are usually in the trivalent state (Cr3+), which like the chromium in the un-corroded steel, is not be a health hazard. There is one very specific example where corrosion may produce very small quantities of hexavalent chromium at ambient temperature. This is where some strong oxidisers with a pH of 10-14 are in prolonged contact with stainless steel and cause corrosion over time.

一旦不鏽鋼受到腐蝕，金屬離子就會被從合金中釋放到周圍環境。這時候析出的鉻離子往往是三價鉻（Cr3+)，它跟未腐蝕的金屬中的鉻一樣對人體是無害的。但是有一個很特殊的情況使得不鏽鋼在室溫下受到腐蝕時會產生極少量的六價鉻，那就是讓不鏽鋼和一些PH值在10-14的強氧化劑長時間接觸並受到腐蝕的時候。

Chromium in stainless steel welding fumes

不鏽鋼焊接煙塵中的鉻

Fumes from welding stainless steels may contain hexavalent chromium ions, depending on the process and any fluxes used.

在焊接不鏽鋼產生煙塵中可能包含六價的鉻離子，這取決於焊接過程和使用的焊劑。

This is described in more detail, separately; fume associated with welding stainless steel

更詳細的描述在另一篇文章：fume associated with welding stainless steel

Efficient local exhaust ventilation systems should normally be suitable for maintaining exposure limits below the 0.05 mg/m3 limit for hexavalent chromium ions.

焊接時應具備良好的通風排氣系統使得六價鉻離子的接觸限值低於0.05 mg/m3這個限值。

Fume associated with welding and cutting stainless steels

標題：焊接和切割不鏽鋼時的煙塵

Fume associated with welding stainless steel 

焊接不鏽鋼時的煙塵

Fume is generated by arc welding processes used for welding stainless steels, both the flux-shielded processes (manual metal arc and flux cored arc) and the gas-shielded processes (tungsten inert gas and metal inert/active gas). Plasma arc cutting also produces fume.

選擇電弧焊對不鏽鋼進行焊接時，不管是在焊劑保護焊（包括手工金屬電弧焊和藥芯焊絲電弧焊）或是在氣體保護焊（包括鎢極惰性氣體保護焊和金屬極惰性/活性氣體保護焊）下焊接都會產生煙塵。使用等離子弧進行切割的時候同樣會產生煙塵。

Fume can be defined as the airborne particles and gases arising during welding or cutting by vaporisation and reaction. Flux-shielded processes form particles of complex composition. Ozone is created by the action of ultraviolet radiation on the atmosphere in the gas-shielded processes. The tungsten inert gas process produces little particulate fume but the metal inert/active gas processes generate both particles and ozone.

隨著焊接或者切割時的氣化反應所產生的煙塵，可以分為空氣微粒和氣體。焊劑保護焊過程中會生成複合物微粒。而在氣體保護焊過程中造成的紫外線會在周圍的空氣中製造出臭氧。鎢極惰性氣體保護焊過程中會產生少量的微粒煙塵，但是在金屬極惰性/活性氣體保護焊過程中會同時產生微粒煙塵和臭氧。

There have been concerns that fume from welding of stainless steels, particularly the particles containing hexavalent chromium formed in flux-shielded processes, is a cause of cancer. Extensive studies over a long period have not supported this view but have nevertheless shown that there is a slight excess of lung cancer among all welders, whether of mild steel or alloy steels. It is therefore sensible to take action to limit contact with welding fume by process selection and/or engineering controls, such as ventilation and extraction. Local fume extraction is more effective than general ventilation. While personal protective equipment such as an air-fed helmet may also safeguard the wearer, it should only be considered for situations such as confined spaces, if only because ancillary workers are otherwise left unprotected.

有人擔心，不鏽鋼焊接時產生的煙塵，尤其是焊劑保護焊產生的微粒含有六價鉻，是癌症的一個誘因。長期的研究表明這個觀點並不成立，但是卻又有證據顯示不鏽鋼焊工在所有的焊工中，不論是碳鋼焊工還是合金鋼焊工之中得肺癌的機率稍微有點偏高。因此，採取合理的焊接工藝或者流程控制來減少對焊接煙塵的接觸是明智的選擇，比如採取通風和排煙系統。採用局部排煙系統比一般通風方式更有效。雖然個人防護用品比如一個空氣頭盔也可能會保護好穿戴者，但它只適合在密閉空間的情形下使用，否則相關的輔助工人就會失去保護。

There is a statutory requirement to control exposure to welding fume, expressed as a general exposure limit for welding fume and OES (occupational exposure standards) and MEL (maximum exposure limits), for individual elements, as specified by the Health and Safety Executive. Sampling to determine exposure is expensive and should only be considered when control measures have been taken and a residual risk has been identified. There are also methods of calculating exposure levels from consumable manufacturers' data.

已經有一些相關的法規來控制人與焊接煙塵的接觸，比如由健康和安全執行機構針對個別元素制定了焊接煙塵的一般接觸限值、OES（職業接觸標準）和MEL（最大接觸限值）。以抽樣的方式確定接觸值成本很高，而且只能在有完備的測量方法並且剩餘量明確的情況下才被考慮。也有從製造商的數據中計算接觸等級的方法。

A typical safety data sheet relating to stainless steel can be downloaded from here.

還有一篇來自美國勞工部網站的文章提到在工業生產中幾種受到六價鉻危害的情況

■Welding and other types of "hot work" on stainless steel and other metals that contain chromium 

對不鏽鋼和其它含鉻的材料進行焊接等高溫作業 

■Use of pigments, spray paints and coatings 

使用顏料，噴漆和鍍膜塗層時

■Operating chrome plating baths 

鍍鉻浴操作時