The development of new rust converter formulations is a relevant issue that contributes to increasing the competitive edge of domestic products and sustainable development of various branches of the economy. The aim of the study is to determine the corrosion resistance of various phosphate films on the metal surface when exposed to salt spray, as well as to determine hardness and resistance to abrasion (scratching).
Materials and methods: Metal rods are coated with a film using a special surface treatment with orthophosphoricacid-based rust converters. The study introduces a new experimental rust converter formulation containing a Lewis acid (or its salts) and dispersed nanopowders of oxide and other inorganic/organic complexes.
Results: Tests revealed that full-scale corrosion of metal rods treated with the experimental formulations began after 9 and 10 days, while untreated rods were showing signs of corrosion as early as on the second day. These films also demonstrated a hardness of 490 HV (modified scale of a TEMP-4 hardness tester) and withstood a maximum indenter load of 4.1 kg (measured with PROMTPP-1518) based on ISO 1518 method (scratching with a needle).
Conclusions: Based on the test results, it was concluded that the modified phosphate films exhibit high hardness and resistance to needle scratching according to ISO 1518 method, and also exhibit increased corrosion resistance to salt spray. However, the demonstrated resistance is insufficient for exposure to a salt spray chamber for 42 days.