Home/Blog/Laser Marking/Black, Corrosion Resistant Marking: Why You Should be Using a Picosecond IR Laser for Dark Marking Applications

Black, Corrosion Resistant Marking: Why You Should be Using a Picosecond IR Laser for Dark Marking Applications

dark marking,black marking,Picosecond IR laser marking, black laser marking, dark laser marking

If you’ve been tasked to find a laser source for a dark marking (or black marking) project, you’ll soon find that while there are a number of available laser sources, not all laser marks are created equal. Black marks made with picosecond IR lasers are superior – in terms of readability and corrosion-and passivation-resistance – to marks made with more traditional lasers, like fiber nanosecond IR and nanosecond UV.  Here’s the scoop.


What is Black Marking?

Defined simply, a black mark is:

  • Dark black in color, with high contrast against its background
  • Corrosion-resistant
  • Permanent, non-fading, no bleeding of color
  • Survives auto-clave or other cleaning or additional passivation
  • Machine-readable
  • Shallow, with minimal surface relief to prevent bacteria accumulation


Who Needs to Make Truly Black Marks?

While many industries and applications – like automotive safety components; aerospace and marine components; and home appliances, such as cook tops, ovens, sinks, and faucets – require permanent, corrosion-resistant, dark marks, they are especially imperative for medical device manufacturers, who need to meet strict FDA-mandated Unique Device Identification (UDI) marking requirements for identification, tracking, and traceability of medical components. Medical devices, like cannulae, catheters and tubes; implantable devices; invasive tools and wires; and operating room/surgical instruments need permanent black marks capable of surviving multiple passivation and autoclaving cycles. For this purpose, our applications engineers have found that ultrashort pulse picosecond infrared (IR) lasers are superior for fast, permanent, reliable black marking.


Where Traditional Marking Falls Short

Medical devices are commonly made of 300-series or 17-series stainless steels due to these materials’ high biocompatibility with the human body, as well as to their mechanical strength, corrosion resistance, and machinability. The naturally-occurring chromium oxide passive layer that forms on stainless steel resists corrosion during sterilization and is inert to the human body.

This passive layer is often damaged during laser processing and other machining steps, making it necessary to do a post-process passivation step to restore it.  This passivation step not only adds time and cost, but also can severely degrade or even erase the marks made using traditional fiber nanosecond IR or nanosecond UV lasers. Why? Because these traditional dark marking techniques rely on thermal processes that leave the passivated material damaged and easily removed in cleaning processes.


Enter Ultrashort Pulse Picosecond IR Lasers

The pulse durations used for picosecond laser black marking are about 10,000 times shorter than the typical pulse durations used for nanosecond laser marking. As a result, they can impart energy to a material surface with minimal thermal effects. Unlike heat-generated annealed marks made by nanosecond lasers, picosecond lasers create marks that are periodic nanostructures – “light traps” – with antireflective properties that make the marks appear deep black against their surroundings.

What’s more, the marks are actually the restructured surface material – not a newly formed oxide layer – so they are highly resistant to bacterial growth, passivation, corrosion, and autoclaving. Another plus – the processing window for making the marks is much wider than it is with traditional fiber nanosecond lasers, not only for stainless steels, but also for aluminum and titanium.

The picosecond IR laser can be integrated into customized CDRH Class 1 systems that are designed for a specific part or range of parts. System features may include a galvo scanning head, a bar code scanner for job load, four or more axes of motion and machine vision for part recognition and mark placement.

dark marking,black marking,Picosecond IR laser marking


Summary: Black Marking with Ultrashort Pulse Picosecond IR Lasers

Ultrashort pulse picosecond IR lasers show a number of benefits that make this the laser of choice for the black marking process. Although upfront costs are higher, the consistency and reliability of the process reduces scrap and increases throughput. Add in the fact that additional processing and testing steps are not required, and the ROI on this type of laser is clear.

Category: Laser Marking