Hot-dip galvanizing certificate
Protection of metal from corrosion, destructive mechanical damage interested people for a long time. In the 18th century the technology of immersion of a metal product in zinc was tested. After almost a century, the method was patented. Today galvanizing is widespread all over the world.
Not every machine that processes steel by means of zinc solution gives a qualitative result. You can check how well and technologically correct the protection of the product is performed in several ways.
Often, when performing the work, the necessary certificates confirming compliance with the GOST galvanizing Are provided. The state standard regulates in detail each stage of steel processing.
It is necessary to begin with preparation of a surface-to degrease, remove the rust rests, to wash out a detail from reagents, to fluxing. Degreasing takes place at a temperature of 60-80 degrees using an acid or alkaline solution. Degreasing stage cleans the surface of the oil, synthetic compounds.
Etching - processing of the material with hydrochloric acid, capable of qualitatively removing rust, scale. GOST requires etching as follows: in a solution of hydrochloric acid concentration of 120-210 g/l to place the item. The acid temperature is recommended 20-25 degrees. After cleaning, wash the product immediately by removing the reagent.
A solution of flux is used more concentrated - 400-600 g/l, and the treatment is carried out at 60 degrees. Fluxing is necessary for cleaning the surface of iron oxide, preparation of metal to the application of a protective layer.
The direct immersion of the steel element in a bath filled with zinc must be carried out according to certain standards. Zinc is heated to 450 degrees. It is this temperature that ensures reliable adhesion of the surface to the melt.
In some cases, after metal processing technology hot dip galvanizing quality certificate is issued instantly. In the absence of a document and there are doubts about the manufacturability of the work, check the thickness of the layer, the strength of the clutch can be separately.
GOST involves two ways to check the thickness of the superimposed mixture:
- application of thickness gauge. The device records the change in the values of magnetic resistance, calculating the actual thickness of the layer;
- on cross section area is to be chosen to test, is examined under microscope. It is optimal to use three sections, calculating the arithmetic mean length.
The strength of the clutch is checked by hammer blows (weight according to GOST is 212.5 grams). The absence of cracks is an indicator of a qualitatively superimposed chemical composition.
Confirmation of hot-dip galvanizing with a certificate is an optional but useful procedure. Only securely protected by corrosion-resistant layer of metals permissible in the construction of many structures.