Post Thumbnail error

Already I lost a night’s sleep trying to figure out how to bring the result of this code correctly. Must return the feature image. Some kind soul can help?

PS: My code return a default image.

What’s wrong?

if ( is_array($main_articles) ) {
    foreach($main_articles as $article) {
        $article = get_post($article); 

        $content.= '<h2 style="font-size:13px"><a>ID) . '" style="text-decoration:none;color:#2D2D25" target="_blank">' . $article->post_title . '</a></h2>';

        $thumb_id = get_post_thumbnail_id();
        $thumb_url_array = wp_get_attachment_image_src($thumb_id, 'full', true);
        $thumb_url = $thumb_url_array[0];

        if ($thumb_url) {
            $content.= '<span>"' . $thumb_url . '"</span>';
            $content.= '<a>ID) . '" target="_blank"><img src="' . $thumb_url->ID . '" width="345"></a>';
        }

        $content.= '<p>' . ptn_shorten_string(strip_tags($article->post_content), 100) . '</p>';

        $content.= '<p></p><a href="' . get_permalink($article) . '">Read more</a></p>';

    }
}
return $content;