Mönchengladbach, May 03, 2018

Smart coating with PERFECT spray®

Thermal spraying conquers new markets

About 1.8 million kilometers of oil and gas pipelines are routed underwater or overland across the whole of Europe. At 4,700 kilometers, the longest pipeline worldwide transports oil from Siberia up to the Pacific coast. The global network of long-distance pipelines includes more than three million kilometers and it is growing each year by approx. 25,000 kilometers. Pipelines which are lifelines supplying the whole world with vital natural resources are indispensable for transporting oil, gas or drinking water over long distances and they are partly subject to extreme conditions. Whether laid on aboveground pipelines, underground or underwater – proper corrosion protection is the essential thing with regard to longevity and resistance of the pipes. Here, the wire arc spraying is used – a method characterized by high deposition rates and low energy consumption.

Wire arc spraying systems of the latest generation

The welding technology experts of SMS group have taken a closer look at it bringing together two promising technologies: wire arc spraying and the fully digital current-voltage source PERFECT arc® developed by SMS group coordinating the control of all electric-arc processes for welding and coating methods without changing the hardware. As a result, the new thermal spraying system PERFECT spray® came into being for treating metal and non-metal surfaces.

With the new wire arc spraying system for thermal spraying acc. to DIN EN 657, SMS group opens up entirely new markets in the areas of corrosion and wear protection as well as for maintenance. Due to control-oriented or design-related disadvantages of the wire arc systems available on the market today, end users had to previously accept major restrictions with regard to the attainable coating quality and process efficiency. Through new approaches in electric-arc control, a new open linear construction type and the development of a new SMS-own burner concept with pressure- loss-optimized, turbulence-reduced and high-expanding nozzle system significant improvements can be achieved in process efficiency and coating quality.

The new wire arc system is of modular design and features ceramic internal flow contours, adapted to the relevant coating task, which were designed to take account of the gas dynamics and can be adapted to the desired gas volume or mass flow rate. There is the option of directing the flow on the wire ends well within the supersonic range (gas flow speeds greater than Mach 1) or of decelerating the gas - depending on the material or application - to subsonic speeds. Almost all metal materials available in wire form can be processed. Through the option of separately controlled wire feed rates it is also possible to process different materials on the cathode and anode sides to generate alloys or pseudo-alloys during the process (e.g. steel/nickel or aluminum/copper combinations).

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CAD image of the optimized arc burner PERFECT GUN (on the left: linear/open type) by comparison with the standard spray burner LD/U2 with its closed design and high pressure losses (on the right)
The more homogenous the spraying process, the better the coating quality

PERFECT spray® offers:

  • an innovative nozzle concept for generating ahigh-speed gas jet
  • a wear-resistant and reliable wire contacting concept
  • precise and ultrafast process control
  • full parameter control of power supply for processingdifferent wire materials and diameters
  • maintenance-friendly burner and durable highlyfunctional materials for all system components

The highlight of the PERFECT spray® system is the active processcontrol by means of fully parameterizable current-voltagesource in connection with active adjustment of the characteristics, depending on each corresponding wire-shaped, metallic filler material.

Thermal spraying method conquers new markets

Current questions and problem definitions of a politically motivated energy turnaround bring coating methods such as wire arc spraying to the fore of such technologies which can ensure a cost-, energy- and material-efficient long-term corrosion protection. Material systems suited for this task definition are alloys based on aluminum-zinc (Al-Zn) which can be processed as pre-alloyed Al-Zn wire or by using different wires (anodic: zinc; cathodic: aluminum). PERFECT spray®, the coating system of SMS group applies a virtually pore-free coating. Due to the possibility of controlling wire feed velocities of cathode and anode separately, materials of different melting temperatures can be conveyed homogeneously, thus setting a constant electric-arc resistance (minimal length variation). In addition, these coatings are post-treated with a specific Sol-Gel-based sealing method ensuring corrosion protection for more than 20 years according to current standard specifications even with heavy seawater exposure depending on coating thickness.

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Corrosion protection coat, 300 µm thick, based on zinc (dark phase) and aluminum (light phase) with a subsequently applied sol-gel seal (see red highlighted area), providing long-term protection for offshore wind turbines.

Wire arc sprayed coatings can also be found in numerous other industrial sectors, such as in automotive industry for coating interior cylinder walls, especially lightweight-construction crankcases in combustion engines, in turbine construction for the application of adhesive primer coats for plasma coating, for repair and maintenance tasks (e.g. for reconditioning shafts and bearing seats), for coating polymer or fiber-reinforced materials (e.g. for improving shielding attenuation characteristics acc. to EMC), in medical technology (among others for antibacterial surfaces), in the aerospace industry (e.g. for wear protection of leading edges), for the polymer industry (heat-conductor layers for local extruder temperature control), in the field of energy production (high-temperature corrosion protection of incineration plants) and in generative manufacturing (coating and functionalization of 3D printed light metals & polymers).

The future-oriented PERFECT spray® predestines the spraying plant not only for applications in the industrial environment but qualifies the plant also for science and research to open up new resource-saving applications and markets. At the largest specialist conference in the field of thermal spraying (International Thermal Spray Conference ITSC-2017) the inverter technology of SMS group and different coating burners were presented to an international expert audience. A specialist lecture in the so-called Industry Forum rounded off this successful event and established SMS group as future- oriented plant manufacturer with innovative products.