Abstract:
In this experimental based research study, Chemical conversion coating, Chromium (Cr) and
Nickel (Ni) electroplating techniques are being used to deposit anti-corrosion protective layers
on ASTM-A516 Grade 17 Steel, which is used in construction and manufacturing industries
most commonly in fabrication of large storage tanks. During the process of chemical
conversion coating which is also known as passivation, Sodium hydroxide (NaOH) and Sodium
nitrate (NaNO3) solution is used as source material to prepare hot alkaline oxide bath solution.
After this process outermost surface of sample is converted into magnetite (Fe3O4). This
magnetite layer prevents substrate surface from any corrosive attack. ASTM-A516 Grade 17
Steel is electroplated with Ni and Cr in which substrate is taken as cathode and metal to be
coated are taken as anode. Chromium tri-oxide and Nickel sulfate are used to prepare
electrolytic bath solution for Cr and Ni electroplating respectively. After depositing the
coatings, Salt spray test is performed on coated and uncoated samples for weight loss analysis,
to evaluate corrosion trends of coated and uncoated samples. The salt spray test serves as a
benchmark for comparative analysis of various samples. In this test, samples are placed in a
controlled environment with specific temperature and humidity levels and exposed to an
atomized 5% NaCl solution. This atmosphere is highly corrosive, leading to surface damage
and accelerating the corrosion process. The results exhibit minimum weight loss in dual coated
(Ni-Cr) samples which indicates high resistance against corrosion. Coated samples micro
structure and surface morphology are studied to further validate result and deduce conclusion.
This is done through X-ray diffraction (XRD), Scanning electron microscope (SEM) along
with energy dispersive spectrometer (EDS) respectively.
