The Blackfast process
The cleaner, Blackfast 716, is an alkaline solution and should therefore not be capable of producing hydrogen embrittlement.
The conditioner, Blackfast 551, is acidic (pH 2.5-3) and contains small amounts of phosphoric and hydrofluoric acid (less than 0.1% in the working solution) and immersion time is no more than 2 minutes.
The blacking solution, Blackfast 181, is also acidic (pH 3-3.5) and contains phosphoric acid and potassium bifluoride (less than 1% in the working solution) and immersion time is only 1 minute.
It is concluded that the Blackfast process contains very low amounts of acid and the immersion times are minimal which should mean that the process is unlikely to cause hydrogen embrittlement.
Coating porosity also has an impact on hydrogen concentration. Electroplated coatings are dense enough to “trap” or seal hydrogen in the base material. Once the hydrogen is sealed in the component, it is more likely to produce an embrittlement failure. Mechanical coatings are more porous (less dense). Therefore, any hydrogen in the base material of a mechanically coated component will have a better opportunity to escape.
The Blackfast process is not a dense coating, rather a surface conversion, and it is specifically designed to produce a porous crystal lattice which will allow oils and waxes to be absorbed into it.
The Blackfast process is therefore unlikely to be capable of trapping or sealing hydrogen in the component.