Title: Naval Laser Coating Removal White Paper
Authors: Donald Sprentall, Kevin Hagedorn PhD, Susan Sprentall
Abstract:
Almost all surfaces need recoating regularly due to aging and environmental conditions that affect the surfaces’ performance. For some items, such as houses, painting over the previous coat of paint is an acceptable practice. However, for other items, such as naval vessels, over-painting is not acceptable because of poor adhesion, added weight, and performance impacts. For these reasons, first it is necessary to remove the existing coating before applying new coating. Making matters more challenging is that in some cases, it is desirable to remove foreign materials from the vessels while leaving the paint undisturbed.
Until recently, there were only three methods for removing coating and/or other foreign matter: manual scraping/chipping/sanding, media blasting, and chemical strippers. Though each of these methods has significant shortcomings, each deemed acceptable, despite the time, cost, and effort needed to prepare the surfaces for stripping.
However, current environmental and cost concerns have rendered these methods unacceptable.
Laser-based methods exist for stripping paint. The advantages associated with this approach address the concerns raised by the use of the traditional methods. Specifically, laser-based methods remove more paint per unit time, have no consumables (other than electricity), produce minimal waste (a volume smaller than that of the paint itself), produce no hazardous waste, use no water, and do not expose operators to hazardous chemicals. The primary concern associated with laser-based methods is a lack of precision – removing more paint than desired. Paint application thicknesses are typically not uniform across the surface, exacerbating the concern
SurClean has addressed this concern with the development of a real-time, closed-loop laser process controller (LPC) and has global patents pending. The LPC analyzes the material being ablated in real time and based on this analysis decides what laser power level is best suited for aggressive coating removal. The LPC modulates the laser power such that high energy emits during paint removal and low (or no) energy emits as the laser passes over the primer and/or substrate.
The LPC has additional attributes that allow use for a broad range of coatings removal applications. Two examples are that the sensing methods used are quite generic, thus the system can be tuned to remove a wide variety of ‘coatings’, such as anodizing, rust, and even biological growths (such as barnacles). Second, there are several, equally effective, means for detecting the differences between the coating removed and the material protected.
SurClean is commercializing the technology starting with handheld and robotic units. The robots will enable completion of large projects e.g. stripping an entire aircraft, stripping ship hulls, superstructure etc. The handheld unit is portable operating from a movable service unit containing the laser and all required systems (power, vacuum, chiller, etc.) for the process. This allows flexibility for forward deployment on ships, at airbases or on Aircraft Carriers. Kuka Systems NA – Aerospace Division is supporting these efforts in the Aerospace industry. In fact, they have provided a working lab featuring the SurClean product which has opened the doors across many market sectors. The NRL has provided samples of the various areas of the ships with a wide variety of coatings. Our equipment removed the coating and through our proprietary optical design, we were able to show the texturizing of the base material which will provide a better adhesion property for the surface coatings applied on aircraft carriers. Funding is approved for Q2 2016 to further explore texturing the surface and establishing a standard for on board surface carriers deck cleaning.