Preparation of Mg and Al phosphate coatings on ferritic steel by wet-chemical method as tritium permeation barrier

Layers of Mg or Al phosphate were prepared on type 430 ferritic stainless steel (SS430) by wet-chemical methods as tritium permeation barrier. Disk-type specimens of SS430 were first coated with ZrO2/ZrO2 or ZrO2/Al2O3 layers (100 nm) by sol–gel and electrolytic deposition techniques. Then, the phosphate layers were prepared by dip-coating method; the total thickness of coating was 200 nm. The permeation rate of hydrogen was measured at 300–600 °C under driving pressure of 0.1 MPa. The Mg or Al phosphate layers provided significant barrier effects, and the permeation reduction factor observed under the present conditions was 200–3000 against that of Pd coated 430 specimen. Further investigation, however, was required to improve the stability at high temperatures.