White spot appears on bright nickel/chrome plated faucet

Helle, I'm a faucet manufacturing company employee in electroplating part.

In summer, I got the product from our warehouse. There was white spot on bright nickel/ chrome plated faucets. There was no problem whit thickness (Ni 10§--, Cr 0.2§--)

It couldn't remove easily, so I used gel-type abrasives to remove it.

I didn't hear white corrosion (like white rust of zinc substrate) of brass substrate.
Is there a any possibility that it can be microbiological corrosion? (In summer season, our warehouse condition is very hot and humid(35¡É. humidity 70~80%) There are also some water remained in faucet.)

Look forward to your reply.

Steve!
To me it sounds like pretreatment solution which comes out from pores in the base material. Take a piece of wet pH indicator paper and put it on the spots. When the spots react alkaline it is strong evidence for pretreatment solution.

greets
Franz

Thank you for reply.

I think It is very simple and clear solution.
I will try and post conclusion!

Best Regard.