Bathtub from 70s-Renovate or Replace ???

I have an old metallic bathtub from 1970s with white enamel which got chipped.

I found a reparation kit(15 euro) and a renovation kit(100 euro), both from www.atmosani.com bought at brico.

(1)Reparation kit is to fix the chip and (2)renovation kit to repaint , both DYI.
(1):
http://www.atmosani.com/espace_pro/pages/entretien-9.html
(2):
http://www.atmosani.com/espace_pro/pages/entretien-6.html

-Has anybody succeeded renovating their old bathtub themselves with above producs?
-Or it is better to replace the bathtub?