Metalizing: Current State of the Art
"Metalizing" is a term applied to pure molten metal-sprayed coats (not paint) as opposed to other methods of applying metallic coatings such as hot dip galvanizing or electroplating. Metalizing equipment is mobile and appropriate for many complex shapes and not limited by size. Metalizing may be used alone or in combination with other coating systems, and drastically increases the adhesion of topcoats when they are applied over metalized coatings. A wide variety of materials can be safely and effectively metalized, including: metal, concrete, glass, plastic, fiberglass, wood, paper, and cloth.
The two principal systems used to protect metal from rust and corrosion are "anodic" and "barrier". A metalized coating such as zinc provides anodic protection in that it forms an oxide and sacrifices itself to protect underlying steel or concrete. The galvanic electro- chemical nature of zinc coatings will retard corrosion on adjacent exposed steel inches away until the last remainders of the zinc coating are consumed. Barrier systems such as paint typically contain numerous microscopic "pin holes". Moisture penetrates these pin holes to reach the unprotected substrate. When this happens, corrosion forms, which expands up to twenty times in the case of steel, resulting in pits and blistering which lift away the barrier coating.
Metalizing is by no means a new technology. It has been in use for the last 100 years. Extensive government and private studies regarding the effectiveness of metalizing are available. They all come to the same conclusion: metalizing is the best corrosion fighting system in the world. Case studies of protection for pipelines, bridges, dams, and marine structure in service over 60 years in various conditions are available from a variety of sources. Salt River Project estimates 100 to 200 years of protection from one 4 mil coat of metalized zinc after a 20 year exposure. The countries of England, China and Japan and the states of Florida, California, Oregon, and Washington use metalizing exclusively to protect their bridges, and the Federal Highway Administration now recommends metalizing rather than painting to protect highway structures. Some of the problems encountered when using old methods of metalizing include: extremely slow speed of application, with a maximum size spray pattern, contamination of the substrate with propane or other consumable gases; necessity of heating the substrate to high temperatures, causing heat related stress fractures in adjacent areas; and difficulty of operation. All of these factors contributed to job costs making slow old metalizing methods costly compared to barrier type coating. IMC's patented new technology is now as fast or faster than airless applied paints. It utilizes a self contained electric arc with no moving parts, except for a safety and remote control switch. The spray pattern can be adjusted from elliptical to circular to fit the size of the object to be metalized. This enables our equipment to spray apply any metal that can be put in wire form, including but not limited to the following: 316 Stainless, Aluminum, Zinc, Hastelloy, Inconel, Copper, and Nickel. The equipment will operate on 220, 380, or 440 volts, and uses clean filtered air to propel the molten metal onto the substrate in a uniform spray pattern followed by near instant cooling and curing.
Because we use only 99.99% pure metals, which are propelled by clean air onto the substrate, we generate no volatile organic compounds and very little overspray. 95% of the material in the spray pattern sticks to the substrate. Metalizing spray tends to wrap around angles and stiffeners, similar to electrostatic paint applications. The metalized coating does not shrink like paint products, which contain solvents, and does not pull away from sharp edges, which is a common problem for "barrier" coatings. Cold substrate temperature is not a factor, enabling applications at near zero temperature conditions. This is especially advantageous in areas such as the North Sea oil fields, where cold temperature applications requiring instant curing are a necessity.
Heat generated from the process dissipates almost immediately upon hitting the substrate preventing any heat transfer to adjacent areas or scoring of areas below the surface. The metal coating does, however, form an ion exchange, creating a molecular bond of alloy metal at the surface rather than simply a mechanical bond, as in the case of paint. The high temperature and velocity of application produce extremely high adhesion bonding to the substrate. Old methods such as flame spray
applications produce bond strengths typically half of those produced by our new method. Paint and other barrier coatings typically disbond and fail when greater than
3-400 pounds per square inch pressure is applied, while our electric arc method exceeds pull-off testing of 6,800 pounds per square inch.
The Environmental Protection Agency gave approval to spray 10 mils of aluminum or zinc followed by 2-3 mils of pure copper on various substrate including steel and concrete to form a permanent anti fouling coating. 4-5 mils of pure copper can be applied directly to fiberglass and plastic to create the same effect. This creates a solid metal coating which is highly abrasion and corrosion resistant, while being impervious to all marine organisms including Zebra Mussels. Studies have shown that copper is the only effective deterrent to Zebra Mussels and is classified as non-toxic. This system is cost effective when compared to anti fouling coatings, which use various forms of poison to slowly leach into water to control organism growth. Most of the oil production companies have now specified metalizing to protect undersea, under insulation, buried, and exposed pipelines for long-term protection. When life cycle costs are considered, the technology is extremely low cost and maintenance free when compared with conventional coatings. Due to the high bond strength obtained, there is no need for touch up due to erection damage from chain or sling abrasion. One oil company projected 50% additional costs when using paint to cover costs of touch up due to erection damage to their piping. We have never had to touch up any of our metalizing due to these factors.
Our new technology provides many advantages:
- Anodic protection
- Speed of application
- High bond strength to the substrate
- High temperature and abrasion resistance
- Increased adhesion of paints as a second coat
- No drying or curing time. Top coats can be applied immediately
- No warping. Heat dissipates immediately
- Environmentally safe
- Proven long term protection
- Competitive application costs
- Can be applied in cold conditions or to cold substrates
Metalizing is a long-term cost effective alternative to conventional coatings, which must be considered for both maintenance and new construction projects.