Hi rtrautman,

Metallizing is more commonly referred to as thermal spraying (THSP), which has several process variations. AWS C2.23M/C2.23:2003 is the Specification for the Application of Thermal Spray Coatings of Aluminum, Zinc, and Their Alloys and Composites for the Corrosion Protection of Steel, and AWS C2.21M/C2.21:2003 is the Specification for Thermal Spray Equipment Acceptance Inspection.

Here's a link to a brief safety and health fact sheet published by the AWS on thermal spraying safety:

http://www.aws.org/technical/facts/FACT-20.PDF

Also, the link below will take you to Chapter 12, which is the Special Applications chapter of the Army's welding site. It should automatically scroll you down to Section III, METALLIZING:

http://www.adtdl.army.mil/cgi-bin/atdl.dll/tc/9-237/Ch12.htm#s3

As far as safety goes, Acetylene cylinder pressures in excess of 15 psi should not be used. When acetylene pressure of 15 psi is too low for the application, another fuel gas should be used. Alloys containing more than 67 percent copper or silver must not be used in acetylene systems because dangerous explosive compounds may be formed. For flame spray guns, a friction lighter, a pilot light, or arc ignition should not be used to ignite the gun. Also, the flame spray gun and its hoses should not be hung on gas regulators or cylinder valves because of the potential of fire or explosion. The plasma and arc methods of thermal spraying pose a hazard because of the presence of high voltages and amperages. The grounding is important, and periodic inspections of the cables, insulation, hoses, and gas lines are necessary, and faulty equipment needs to be replaced immediately. The entire system must be shut down before repairing any part of the power supply, console, or gun. Arc spray guns should be cleaned frequently to prevent the accumulation of metal dust. If the plasma or arc spray gun is suspended, the suspension hook must be insulated or grounded. Contact between any ungrounded portion of the plasma or arc spray gun and the spray booth or chamber must be avoided. Obviously, fire prevention would be a concern, because airborne finely divided solids, especially metal dusts, must be treated as explosives. To minimize danger from dust explosions, adequate ventilation should be provided to spray booths. A wet collector of the water wash type is recommended to collect the spray dust. Good housekeeping in the work area is important to avoid the accumulation of metal dusts, particularly on rafters, tops of booths, and in floor cracks. Paper, wood, oily rags, etc. can cause a fire if not removed prior to operating the equipment. The general requirements for the protection of thermal spray operators are helmets, hand shields, face shields, or goggles to protect the eyes, face, and neck, (ANSI Z87.1 and Z89.1). Safety goggles should be worn at all times. Helmets, hand shields, or goggles must be equipped with suitable filter plates to protect the eyes from excessive ultraviolet, infrared, and intense radiation. Depending on which process, these filter shade numbers can range from 2 to 12. Most operations require the operator to use a respirator. The nature, type, and magnitude of the fume and gas exposure will dictate which type of respirator to be used, and the selection should be in accordance with ANSI Z88.2. Ear protectors or ear plugs that reduce the noise level below 80 decibels should be worn to protect the operator from high intensity noise from the gun. Appropriate clothing needed for the operation will vary with the size, nature, and location of the work. When working in confined spaces, flame resistant clothing, as well as leather, rubber, or asbestos gauntlets should be worn. Clothing should be fastened tightly at the wrists and ankles to keep dusts from contacting the skin. For work in the open, ordinary clothing such as jumpers or overalls can be worn, however open shirt collars and loose pocket flaps are potential hazards. High top shoes should be worn, and cuffless trousers should cover the shoe tops. The intense ultraviolet radiation of plasma arc spraying can cause skin burns through normal clothing. When using this process, the clothing such as thick, tightly woven wool may suffice. For exposure to more intense radiation, leather capes may be necessary. Protection against radiation of arc spraying process is the same as that used for normal arc welding.
If you have access to Volume Three, Seventh Edition of The Welding Handbook, Chapter 12 is devoted to Thermal Spraying. It has a wealth of information on the subject, from fundamentals, explanations of process variations, preparations, post treatments, surface finishing, properties, and applications, to safety.
Incidently, I'm not trying to set a Guiness record for the world's longest post, I just don't have anything better to do at the moment.

It has been a while but we have done some metallizing with 85/15 Zinc-aluminum. The application gun used twin wires and an arc between them. Compressed air propelled the metal droplets to the surface. It has been so long that I forget the correct terminology.

We sprayed ours inside a paint bay (volatile materials were removed first of course) that has positive ventilation to the outside. Applicators wore fresh air supplied masks.
Ear protection is a must with any of the thermal spray processes and you might want to seriously consider ear plugs AND ear muffs. I remember that it was at least as loud, or louder than an air arc.

The clean-up wasn't too bad. There is a lot of "overspray" but it sweeps up easily and didn't seem to cause major dust clouds. I don't recall having to treat the sweepings as hazardous waste.

I would contact Pratt Brothers who makes the 85/15 wire. They were very helpful in getting us set up for the job. They want you to succeed because then they sell more wire, but they didn't try to push us in directions we didn't want to go.

Chet Guilford