Metals Flashcards
Metals
Chemical element that is a good conductor of electricity and heat and forms cations (positively charged ions) and ionic bonds (salts) with non-metallic elements
Classification of Metals
Ferrous and non-ferrous metas
- common ferrous: irons and steels
- common non-ferrous: Al, Sn, Cu, Zn
Precious and non-precious
Metals and Good Health
Essential metals in body (Na, K, Ca, Mg)
Required in trace amounts for essential processes:
- bind with and activating enzymes (Mg, Mn)
- assist in carriage of O2 (Fe haemoglobin)
- assist in nervous system and muscle contractions (Ca, Na, K)
Adverse health effects when levels exceed or below requirements
Sample Analysis
Sample analysis first involves gravimetric analysis of filters for total mass
After weighing, sample is dissolved in acid for analysis, filter type is important
Analytical methods include:
- Atomic Absorption Spectroscopy
- Inductively Coupled Plasma
- Mass Spectroscopy
Fumes
Very small airborne particles commonly formed from condensing vapours from burning or melting materials
- Metal fume exposure is associated with a range of acute and chronic occupational illness
Welding Fumes
Mixtures of airborne gases and fine particles
Degree of risk will depend on:
- composition of fume
- quantity of fume in breathing air
- duration fo exposure
Composition depends on:
- Consumables: electrodes or filler metals, heating or shielding gases and fluxes
- Composition of material and any coatings
- Operating conditions
Metals in Welding
MANGANESE (Mn): most stainless steel carbon alloys, welding electrodes
CHROMIUM (Cr): alloying agent in stainless steel, chromate generate in welding stainless steel
LEAD (Pb): metal coated with lead or lead based paint
CADMIUM (Cd): protective coatings
VANADIUM (Va): in certain alloys and welding electrode coatings
ALUMINIUM (Al): less hazardous, avoid inhalation of fumes
COPPER (Cu): in many alloys (e.g. brass and bronze)
IRON (Fe): common in fumes. Acute effects include respirable irritation
NICKEL (Ni): many alloys and steel, causes acute effects, eye and throat irritation
ZINC (Zn): welding galvanised or Zn plated metals can result in the inhalation of ZnO fumes and cause metal fume fever
MOLYBDEMUN (Mo): found in some steel alloys, causes bronchial irritation
Welding Fumes (Main Effects)
Irritation of respiratory tract
Metal fume fever
Systematic poisoning
Long term or chronic effects
Lead (Pb)
Soft malleable metal with good anticorrosive properties
- inorganic lead: lead metal, inorganic (non-carbon) lead compounds and lead salts of organic acids
- Organic lead: lead combined with an organic molecule
Lead Toxicity
Acute effects are rare, mainly cumulative chronic poisoning
Chronic effects: range from stomach pains to lethargy and anaemia
Inorganic Lead (Effects)
Early symptoms: fatigue, headache, aching bones, and muscles, constipation, abdominal pains, decreasing appetite
Later symptoms: anaemia, pallor, ‘lead line’ on gums, kidney damage
Decreased hand grip and foot extensor strength, characteristic ‘wrist and foot drop’, peripheral neuropathology
Acute poisoning: ingestion and inhalation of large amounts –> severe headaches, convulsions, coma, delirium, and possible death
Controls
Effective engineering controls (e.g. local exhaust ventilation ) are important
Lead register and management program
Health surveillance
Training program: personal hygiene and other work practice controls
Full body clothing, gloves, eyewear, RPE
Require shower and changing clothes at end of shift
Vanadium (Potential Occupational Exposure)
Ferro-vanadium
V2O5 (vanadium pentoxide) used as industrial catalyst in glass and ceramic glazes, welding and electrode coatings
Other vanadium compounds used in dyeing, insecticides, as catalysts and in metallurgy
Oxides produced during smelting and refining
Vanadium (Routes of Entry and Health Effects)
Inhalation of dusts or fumes
Most common: irritation of eyes and respiratory tract
Asthma-like, acute bronchitis, bronchospasm, chest pain persistent and productive cough and wheezing
Serious acute exposures may cause pulmonary oedema and pneumonia
Green discolouration of tongue from V2O5
Vanadium (Personal Protective Methods)
Protective clothing/gloves help prevent dermatitis
Training in personal hygiene
Showing after each shift, change into street clothes
Clean work clothes daily
