Abstract :
Corrosion damage may, from the technical point of view, cause changes in mechanical and physical
characteristics in particular, at the same time it may also cause changes in surface geometry. These
aspects are likely to manifest themselves in all steel parts. The presented study looks at corrosion
protection in bolts and bolt connections protected by metal coating based on zinc.
Four diff erent types of passivation, easily accessible on the Czech market, have been selected for this
experiment. They are as follows: fi rst, galvanic plating using white zinc; second, galvanic plating using
yellow zinc; third, hot dip galvanizing; fourth, specifi c type of plating using the technology Dacromet
500 LC. In order to compare the given parameters there have been selected a unifi ed M bolt size of
8 × 30 mm.
The experimental part of this study can be further divided into two phases. The initial phase puts
stress on the exact specifi cation of the protection layer, namely, the analysis and establishment of the
elemental compositon contained in the given coating, its microhardness, weight and thickness. The
second phase of the experiment analyses the results of tests according to the norm ?SN ISO 9227 (Salt
Fog Test) and ?SN ISO 6988 (Sulphur Dioxide Test). With the tests we have concentrated on the initial
stages of corrosion degradation and its overall process.
