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Metals
Handling, storage and display guidelines
When you are handling metal objects, particularly ones with polished surfaces, always wear clean cotton gloves or surgical gloves. This prevents the transfer of sweat and fats from the skin to the metal object, and helps reduce the risk of corrosion.
Always give your objects adequate support, and remember that metals can weaken over time.
Don't lift metal objects by their handles. The joint between the handle and the object could be weak.
When displaying a hinged object open, take care to support it—so that the hinges are not carrying the weight of a part or all of the object.
Because some of the major contributors to the deterioration of metals are oxygen, water and air-borne pollutants, it is important to provide an environment which offers protection against these factors. This action can prolong the life of your metal objects.
Simple steps can greatly improve the longevity of objects. Steps such as:
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wrapping objects in unbuffered, acid-free tissue;
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placing them in acid-free boxes; and
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storing them on painted—preferably baked enamel—metal shelving.
| CAUTION: |
| Avoid chipboard or wood cabinets. These materials give off formaldehyde and organic acid vapours, which can accelerate corrosion. |
If you have no choice about the type of shelving and you must use wooden shelves, we recommend you take the following steps:
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coat wood with an epoxy or polyurethane finish to seal the wood;
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paint chipboard with a solution of 400g of urea in 1 litre of water; and
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allow time for proper drying and curing.
Do not seal objects in plastic bags, because the bags seal in moisture as well. This raises the relative humidity inside the bag, providing a microclimate which is favourable to corrosion.
| CAUTION: |
| Avoid polyvinyl chloride—PVC—bags. They can give off hydrogen chloride, an acidic gas which will corrode most metals. |
If you want to use plastic bags for storage, make sure you select polyethylene bags, and punch holes in the bag.
Store and display metal objects in environments where:
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the temperature is stable—remember that fluctuations in temperature can cause the relative humidity to fluctuate;
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relative humidity is less than 45%.
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lighting levels are kept below 300 lux. Lighting levels should be lower if the objects are coated, because the light can adversely affect the coating; and
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UV content is below 75 µW/lm.
| For more information |
| For information about adverse environmental effects, please refer to Damage and Decay. |
Corrosion can be stopped by removing oxygen or water from the local storage environment. Reasonably small, particularly vulnerable objects can be placed in a container with silica gel or an oxygen scavenger. Removing only one element of the corrosion equation, effectively halts corrosion—including bronze disease.
Guidelines for outdoor objects
If you are trying to prevent corrosion in an outdoor object:
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bring the piece inside, or build a roof over it, if it is appropriate and possible. In most cases this won't be possible;
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look for areas where water can pool, and improve the drainage in these areas or remove water after rain;
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don't allow objects to sit directly on grass—raise them on a plinth;
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don't allow the object to sit in water;
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don't water the object when you are watering the garden—unlike the plants, it won't grow; and
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clean off bird excrement immediately—it is corrosive and will quickly etch the surface.
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