Dehydrogenation is a process that removes the hydrogen generated during the coating process to prevent it from causing brittleness in the parts.
The problem with many steel grades is the hydrogen absorbed into the base material during surface treatment.
This phenomenon can cause unpredictable brittleness in the metal structure and cause significant damage.
Proper heat treatment as soon as possible after coating can reduce the risk of hydrogen embrittlement.
Heat treatment in Pinnoitus Helin Oy
- 2 pcs of circulating air furnaces
- max.
250 C - 1500x1000x800 mm
Standard:
- Post-coating treatments of iron or steel to reduce the risk of hydrogen embrittlement.
(ISO 9588:2007)
According to the standard, heat treatment should start no later than 3 hours after the coating is finished.
The same standard also specifies the duration and temperature of the treatment.
The standard dehydrogenation of fasteners such as screws and bolts is 3 hours at 220 degrees.
The risk of hydrogen embrittlement in surface treatment arises in any chemical process where hydrogen is formed on the surface of a piece.
In the best case, hydrogen atoms combine and are released as hydrogen gas into the air.
However, some of the H+ ions are absorbed into the object and have a structurally weakening effect.
According to the standard, pieces with a tensile strength of less than 1000 MPa do not need to be heat treated, but in many cases this is the practice.
For thick zinc layers, a two-step process is often used, with the first galvanising being carried out at approx.
A two-stage process is often used, whereby the first step is carried out to a thickness of 5 µm, followed by the required heat treatment and finally the coating to the desired thickness.
This is based on studies which have shown that hydrogen removal is impeded if the zinc layer thickness exceeds 10 µm.
In hydrogen embrittlement, it should be noted that the phenomenon is not unambiguous.
In particular, for components whose intended use is critical to the safety and functionality of the whole, the problem of hydrogen embrittlement must be examined on a case-by-case basis.