  Classical Cepheids (DCEPs) are crucial for calibrating the extragalactic
distance ladder, ultimately enabling the determination of the Hubble constant
through the PL and PW relations they exhibit. Hence it's vital to understand
how the PL and PW relations depend on metallicity. This is the purpose of the
C-MetaLL survey within which this work is situated. DCEPs are also very
important tracers of the young populations placed along the Galactic disc. We
aim to enlarge the sample of DCEPs with accurate abundances from
high-resolution spectroscopy. Our goal is to extend the range of measured
metallicities towards the metal-poor regime to better cover the parameter
space. We observed objects in a wide range of Galactocentric radii, allowing us
to study in detail the abundance gradients present in the Galactic disc. We
present the results of the analysis of 331 spectra obtained for 180 individual
DCEPs with a variety of high-resolution spectrographs. We derived accurate
atmospheric parameters, radial velocities, and abundances for up to 29
different species. The iron abundances range between 0.5 and -1 dex with a
rather homogeneous distribution in metallicity. The sample presented in this
paper was complemented with that already published in the context of the
C-MetaLL survey, resulting in a total of 292 pulsators whose spectra have been
analysed in a homogeneous way. These data were used to study the abundance
gradients of the Galactic disc in a range of Galactocentric radii spanning the
range 5-20 kpc. For most of the elements we found a clear negative gradient,
with a slope of -0.071\pm0.003 dex kpc^-1 for [Fe/H] case. Through a
qualitative fit with the Galactic spiral arms we shown how our farthest targets
(R_GC>10 kpc) trace both the Outer and OSC arms. The homogeneity of the sample
will be of pivotal importance for the study of the metallicity dependance of
the DCEP PL relations.
