iPhone 6 problems with warranty and humidity

I have a dead pixel on my iphone 6 and sand to service during the warranty and the service sad that if is hi humidity outside or foggy weather my phone can oxidate

and they do not recognize my warranty but they do not know from what my phone oxidate so my question is is the iphone 6 low quality product that can oxidaty during hi humidity outside bicause they tall me all same answer the do not know how it oxidate but it is