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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Detonation spraying | 3/3 | https://en.wikipedia.org/wiki/Detonation_spraying | reference | science, encyclopedia | 2026-05-05T10:47:14.991060+00:00 | kb-cron |
Detonation spraying creates a coating that is mostly mechanically bonded as opposed to being metallurgically bonded, which is a much stronger type of bond. Detonation spraying is a 'line of sight' process meaning that components generally need to be coated before being put to use or assembled. This is because the detonation gun needs to be able to access the surface to be able to apply an effective coating. The coatings despite being considerably strong in compression are weak under tension, meaning they can't be applied to malleable or expanding components. The coatings tend to fatigue under pinpoint loading. Detonation guns are quite large and loud. Detonation spraying has to be performed at a location specifically designed for it, as the gun is reasonable large and it is a loud process that produces substantial noise. For this reason, it is usually installed in a sound-proof room (with concrete walls 45 cm thick). The process involves a considerable amount of mechanisation and automation because the operator can't be in the room whilst the D-gun is in operation.
== Safety == Detonation gun spraying like any other industrial process carries with it a number of safety hazards that need to be managed correctly in order to ensure operator safety whilst in use. These safety precautions primarily fall into the following categories and the hazard minimisation techniques suggested, in some cases have a positive effect on the resultant detonation spray coating. For example, having to automate the spraying process means that a very even and consistent spray coating can be achieved.
=== Noise === The operation of a detonation gun is a very loud process due to the multiple explosions occurring in the chamber per second. This could cause damage to operators hearing if in close proximity to the D-gun. As a result, detonation spraying should be performed within a sound proof room and no one should be present in the room during operation. Also operators should wear ear protection (such as ear muffs and/or ear plugs) while working with a D-gun.
=== Heat === Extremely high temperatures are reached by the D-gun (≈4000 °C) whilst in operation. Flammable and explosive fuels (generally acetylene) are used in detonation spraying to produce the supersonic shockwave that propels the powder coating materials onto their target components. This poses a serious burn and explosion hazard. Again, no-one should be present in the room whilst the D-gun is in operation and the room should be designed to withstand any malfunction of the D-gun. Also protective gloves should be used to handle the D-gun and sprayed components to avoid burns from hot components after spraying.
=== Dust and Fumes === The D-gun atomises the powder feedstock into extremely small particles (80–95% of particles by total number are of size <100 nm). This means proper extraction facilities are required for inhalation safety purposes. Also isolation of the D-gun is recommended to avoid operators breathing in the dangerous dust and fumes. If operators are to enter the room they should wear appropriate dust masks or respirators. Many of the compounds used as the feedstock in detonation spraying are detrimental to human health if ingested or inhaled. Airborne metals from the detonation gun in particular are harmful to the lungs. Exposure to cadmium for example can cause harm to the kidneys and lungs, vomiting, loss of consciousness and even reduced fertility. Also heavy metals have been shown in recent studies to be carcinogenic such as lead, nickel, chromium, and cadmium. Some serious lung conditions caused by metal dust inhalation include:
Silicosis - a lung disease cause by inhaling silica present in the feedstock compounds. Siderosis - (silver polisher's lung or welder's lung), a lung disease cause by inhaling iron present in the feedstock compounds. Alzheimer's - a memory loss disease more common among the elderly has been shown by some studies to be caused by high levels of exposure to aluminum (among many other causes). However, these studies were not conclusive, and others have proven otherwise. Metal fume fever - this can occur in some individuals following exposure certain metal compounds (such as copper, zinc, magnesium and aluminum alloys or oxides) that have a particularly unpleasant odour. The fumes are caused as a byproduct when the metals are heated and can trigger a fever-like reaction that may need medical attention.
== References ==