Frequently Asked Questions

(Answered from the published papers on metalizing)

How does arc sprayed metal differ from flame sprayed metal?
"The use of the electric arc process is often preferred to the flame process because it results in higher deposition rates and bond strength."
Publication:  AS/NZS 2312 - 1994, Section 6.3.2

How much faster than plasma spray is the IMC arc spray process?
"Consider a typical example in which conventional plasma equipment was used to spray a paper roll measuring 3' in diameter by 20' long (.91 m by 6.1 m).  In order to complete the job quickly, the customer used six plasma guns to finish the job in 8 1/2 hours."  (TAFA website.)  THE IMC ARC SPRAY PROCESS COATS UP TO 80 m2/hour.

Aren't thermally sprayed metal coatings porous?
"Porosity is sealed by normal aging, through formation of salts of the component metals (oxides, hydroxides, carbonates, etc.).  Sealing and/or painting can be used to prolong the service life of a metal sprayed coating."
Publication:  ISO 2063, Annex B, Section B.1

How does Zinc protect steel?
"Both Zinc and Aluminum are anodic to steel.  Zinc affords greater electrolytic activity than Aluminum, providing good galvanic protection to steel exposed in the atmosphere.  Breaks in the coating are protected by the galvanic couple, that is, the Zinc corrodes, rather than the structural steel."
Publication:  Page 23, ROADS & BRIDGES, August, 1986.

How does Aluminum protect steel?
"Aluminum is less active than Zinc.  Aluminum's protection of the substrate relies more on a thin oxide film.  This characteristic gives distinct advantages in low pH (acidic) and chloride environments.  Because Aluminum is less active than Zinc, it cannot protect breaks in the coating."
Publication:  Page 23, ROADS & BRIDGES, August, 1986.

What is the long term testing history of thermal sprayed coatings in marine environments?
"Both 80 and 150 micron Aluminum coatings showed no corrosion of the steel substrate after 34 years exposure at the LaQue Centre (Kure Beach, North Carolina) test site.

Bethlehem Steel Corporation documented the results of 25 years' experience with Al/Zn alloy coatings, also at LaQue.  The time to first rusting of the substrate was 15 years for severe marine (25 m from ocean) and 25 years for moderate marine (250 m from ocean).

The Norwegian Institute for Air Research published the results of metalized steel exposed 14.5 years in a marine splash zone (Tanager, Norway).  A 160 micron Aluminum coating had visible but no significant damage.

Experience in the Soviet Union showed that a 120 micron Aluminum coating could perform effectively for 20-25 years in salt water.  A 150 micron dual Zinc/Aluminum coating could last 40 years or more in a humid environment.

Testing at SINTEF, Norway, in natural seawater gave free corrosion rates of 2 to 3 microns per year after 11 months of exposure for both Al and Al 5% Mg.  This would imply a service life of 60 years for a 200 micron thermal sprayed Aluminum coating."
Publication:  Page 28, MP, April, 1995.
Authors:  Karl P. Fischer, William H. Thomason, Trevor Rosbrook, Jay Murali

What is the structural integrity of sprayed metal coatings?
"The density of sprayed metals is typically 85% to 95% of the density of the wire from which it is sprayed.  The total oxide included in the sprayed film accounts for only 0.5% to 3% of the reduction; the density reduction is due primarily to the characteristic porosity of sprayed metal coatings."
Publication:  Journal of Protective Coatings and Linings, August, 1989, Page 39.
Author:  Tim Race, Vince Hock and Al Beitelman, US Army Construction Engineering Research Laboratory

What are the economics of thermal spray (TS) metal coatings?
"Application of TS coatings shows considerable savings compared to conventional coatings.  Multiple coat systems require dry times between each coat, and final cure time before parts can be handled without damage.  TS coatings can be sealed immediately after coating and, if a top coat is desired, it may be applied within 4 hours."
Dynamic Coatings Corporation Web Page

"Each process has different costs, materials flexibility and coating performance capabilities.  As a surfacing technology, however, thermal spray is compatible with most materials, is affordable, rapid, and can produce relatively thick (0.010" to 0.00110") protective coatings."
Drexel University Web Page (Philadelphia, PA, USA)

How many types of metal can be sprayed?
Any metal which can be obtained in wire form can be sprayed, including copper, stainless steel, hastelloy, inconel, and monel...even silver and lead!

Both Zinc and Aluminum are anodic to steel and provide cathodic protection at the economics of barrier coating.

Applied in Lenticular Splats, the molten metal is permanently bonded to the substrate.

Utilizing electric arc methods, any substrate can be metalized including concrete, fiberglass, wood, and clay.

Is there a question that you would like to see answered on here?  Ask us, and we'll do our best to answer it and post it for all to see!