Preheating of API 5L Pipe Before Blasting During 3LPE Coating

1.Why preheating is done before 1st blasting,is it to remove moisture what are other

reason.As after blasting there is process of phospate application and than DI water wash,so any how water is used again for wahing of phosphate soln and then 2 nd blasting is done.

2.why Chromate Application is done on blasted pipe before Epoxy coating