Hey,
I just rendered this object into images. Object is deconstructed into 3 png files and I got this weird white gap around object on every png. Does anybody have solution for this? It is clearly visible around suitcase lock.
Thank you very much for your time. 
Hello, I don’t have really an answer but a clue and maybe a solution.
https://docs.blender.org/manual/en/latest/glossary/index.html#term-Alpha-Channel
I rendered, in Eevee, a cube then another cube closer to the camera with the Render Properties > Film > Transparent toggle on. Then loaded the two into the compositor and found the same thing. In the second image the premultiply control is all the way on. Hopefully that will help.
That is probably anti-aliasing. This is a common technique that is used to “soften” the edges of things to prevent “jaggies.” The alpha is adjusted at the edge of the object. If you don’t account for it, you can see the outline.
Just do an internet search on that term … and, here at this site.
Image-format files such as PNG and JPG commonly use anti-aliasing.
Thank you for your answer. I tried this but it didn’t help. Here is mine composition in blender. I’m rendering it in cycles so dunno if that is the problem.
I’m rendering each object on separated layer in blender and than saving it thought this method. I’m going to try render just one object (render layer > alpha over > composite) and I will let you know.
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Haha … it worked. The software that I was using to put object together has bug with png files and it will make weird outlines to objects. So this composition in upper image works
Thank you and have a great day everyone! 
Glad you sorted it out.
