  London penetration depth, $\lambda(T)$, was measured in single crystals of
SrFe$_2$(As$_{1-x}$P$_x$)$_2$ ($x=$0.35) iron - based superconductor. The
influence of disorder on the transition temperature, $T_c$, and on $\lambda(T)$
was investigated. The effects of scattering controlled by the annealing of
as-grown crystals was compared with the effects of artificial disorder
introduced by 2.5~MeV electron irradiation. The low temperature behavior of
$\lambda(T)$ can be described by a power-law function, $\Delta \lambda
(T)=AT^n$, with the exponent $n$ close to one in pristine annealed samples, as
expected for superconducting gap with line nodes. Upon $1.2 \times 10^{19}$
\ecm irradiation, the exponent $n$ increases rapidly exceeding a dirty limit
value of $n=$ 2 implying that the nodes in the superconducting gap are
accidental and can be lifted by the disorder. The variation of the exponent $n$
with $T_c$ is much stronger in the irradiated crystals compared to the crystals
in which disorder was controlled by the annealing of the growth defects. We
discuss the results in terms of different influence of different types of
disorder on intra- and inter- band scattering.
