Abstract
The original cavitation erosion resistance of various metallic coatings has been investigated with the measurement of the natural electrode potential of test pieces under cavitation condition on the magneto-striction vibrator.
The cavitation fatigue diagrams (S-N diagrams) which relate to stress amplitude and repeated number have been investigated about various metallic coatings on cast iron.
The order of resistance to cavitation is as follows:
Electroplating of triple layers with bronze (25μ), Ni(25μ) and Cr(7μ)>SUS27 metalicon>electro plating with bronze (20μ)>Al hot dipping>Zn metalicon.
A few coatings were applied to prevent cavitation pittings to MAN type engine cylinder liner in inhibited coolants.
The results of these tests showed the electroplating of triple layers with bronze, Ni and Cr proved to be free from cavitation-corrosion damage, and stainless steel metalicon, Al hot dipping and Zn metalicon were partially damaged after about 200, 000km running. The maximum depth of pitting was estimated to be 1.5-3.0mm/200, 000km running, and no crack was observed in these damaged parts.
