Update
As of version 3.2, there exists two new commands which can be used to define directly the keyword title and the abstract title, i.e. \keywordtitle
, and \abstracttitle
.
A better setup is as follows
\documentclass{elsarticle}
\usepackage[T1]{fontenc}
\usepackage[english,french]{babel}
\usepackage{caption}
\usepackage{regexpatch}
\DeclareCaptionLabelSeparator{frenchcolon}{~: }
\captionsetup{labelsep=frenchcolon}
\keywordtitle{Mots cl\'es}
\abstracttitle{Résumé}
\keywordtitlesep{~:\/}
\makeatletter
\xpatchcmd{\printFirstPageNotes}
{Email addresses}
{Adresses email}
{}{}
\xpatchcmd{\printFirstPageNotes}
{Email address}
{Adresse email}
{}{}
\regexpatchcmd*{\printFirstPageNotes}{:}{\cA:}{}{}
\regexpatchcmd*{\keyword}{:}{\cA:}{}{}
\makeatother
\begin{document}
\begin{frontmatter}
\title{Titre}
\author{Auteur}
\ead{a@b}
\begin{abstract}
Le r\'esum\'e
\end{abstract}
\begin{keyword}
Les mots cl\'es
\MSC{AAA}
\end{keyword}
\end{frontmatter}
\section{Aaa}
Texte
\begin{figure}[htp]
\caption{L\'egende}
\end{figure}
\begin{table}[htp]
\caption{L\'egende}
\end{table}
\end{document}
Original answer
I'm not sure if elsarticle
is meant to be used with languages different from English, because several English words are hard coded in it.
Here is a possibly not complete patch for making the class into using French for the tags.
\documentclass{elsarticle}
\usepackage[T1]{fontenc}
\usepackage[english,francais]{babel}
\usepackage{regexpatch}
\makeatletter
\xpatchcmd{\abstract}{Abstract}{\abstractname}{}{}
\regexpatchcmd*{\@makecaption}{:}{\cA:}{}{}
\xpatchcmd*{\keyword}{Keywords}{Mots cl\'es}{}{}
\regexpatchcmd*{\keyword}{:}{\cA:}{}{}
\xpatchcmd{\printFirstPageNotes}
{Email addresses}
{Adresses email}
{}{}
\xpatchcmd{\printFirstPageNotes}
{Email address}
{Adresse email}
{}{}
\regexpatchcmd*{\printFirstPageNotes}{:}{\cA:}{}{}
\makeatother
\begin{document}
\begin{frontmatter}
\title{Titre}
\author{Auteur}
\ead{a@b}
\begin{abstract}
Le r\'esum\'e
\end{abstract}
\begin{keyword}
Les mots cl\'es
\MSC{AAA}
\end{keyword}
\end{frontmatter}
\section{Aaa}
Texte
\begin{figure}[htp]
\caption{L\'egende}
\end{figure}
\begin{table}[htp]
\caption{L\'egende}
\end{table}
\end{document}

The annoying warning will still show up. You can remove it by adding also
\usepackage{silence}
\WarningFilter{frenchb.ldf}{Figure}
\frenchbsetup{CustomiseFigTabCaptions=true}
in your preamble?