Blackening is a process of chemically transforming the surface of a metal (usually steel, but also other ferrous metals such as iron, aluminium and zinc) to a black oxide. Oxide is basically another given term relating to what is called rust, but if it forms in the right kind of atmospheric conditions, it will create a structurally patterned form of rust which is then called oxide. The blackening process that has been commonly used over the past 50 – 60 years is known as the hot process. This has been the most popular method utilised during that time period and means that a blackening solution temperature is elevated to 285 degrees to accomplish the black oxide process.
As most of you are aware, water happens to boil at 212 degrees Fahrenheit, so, this process has been performed by professionals and experts in their trade for quite obvious safety reasons, and their seasoned experience will give you a professional final finish.
Cold Temperature Blackening Process
The other possible and becoming more popular way that many people have come to utilise, is called a cold or room temperature blackening process. This form of chemical metal blackening can be found in professional workshops and is usually somewhat cheaper. Some workshops offer both methods which give the customer the choice of method they prefer.
Blackening is also just another name for what was a long time ago called bluing. Bluing is an old name usually referred to when finishing a gun barrel or part. The chemical that was used for bluing in the old days has since been outlawed. So that these days there really isn’t any true bluing going on any more like you see on older guns. Should you request for a gun part to be blued, you are actually getting a blackened part.
What are the Major Benefits of Blackening?
- Superb finish for parts that can be shelved for later processing
- No dimensional (tolerance) change. No additional tolerencing is required for design when finishing parts with this method
- The thickness of the coating is a mere 10’s of millionths of an inch thick
- Extremely cost effective process and especially so nowadays
- Great efficient corrosion protection
- Improvements in lubricity
- Nice aesthetic and decorative finish
- A good reduction in light glare
- Pre-treatment for paint
- Great conductivity is still retained
- No worries about any kind of brittleness or pitting occurring
- None of those awful welding fumes
The industrial room temperature blacking process is an uncomplicated dip procedure which is especially worked out for use in factories. This method results in a uniform colouring which covers completely over all machined nooks and crannies. Blackening is brought to a successful conclusion by the chemical transformation of the metal surface. The whole process requires a process of degreasing, immersion in a surface conditioner, and then blacking solution. Corrosion protection is then made possible by a final baptism in a dewatering oil.
Blackening is certainly an advantage for maximum benefits to all metals it touches.