How poor pretreatment affect plating effort?

I recently done electroless plating for nickel and I would like to know what poor pretreatment will lead to and the subsequent of the article to corrosion .

Poor pretreatment tends to lead to poor adhesion. This may be seen in various forms such as flaking plating, blistering (especially evident after heat treatment), pinholing, even larger voiding as well as having the potential to do a lot of harm to the plating solution, which, if the wrong contaminant is carried across may even seed out (where all the nickel drops out of solution).

The effects on corrosion resistance will be disasterous. Nickel works as a barrier protection (unlike zinc or cadmium, they act as secrificial coatings), so any breaches of the coating are going to cause failure in a very short period of time.