Sulfate in splice 12v

Hi guys. I want to know your opinion about this. e seen in several cases sulphate in splice. It always occurs in 12v power cables (approx 4amp). always coated with DR-25 and ATUM. Could it be that the brass terminal produces this? Did it have to be tinned copper? I am seeing it in a harness older than 2 years of constant use. It is a KTM 450 SXF race harness

Brass does develop a green coating when exposed so it's more visible than other materials, but tracing the root cause back it looks like perhaps the DR25 wasn't completely sealed up? It's hard to say from the picture, but getting the harness completely sealed from the elements may solve this.