Methods of applying a polymeric coating to a rear face surface of golf club heads with variable face thickness are disclosed herein. The coating, which preferably comprises polyurea, improves the durability of the face and reduces the hits to failure ratio of the golf club head. The coating improves the performance of the golf club head because it allows for reduction in overall face thickness and easy post-process manipulation to allow for fine-tuning of mass properties after production. The reduction in thickness leads to overall weight reduction, because the polymer is roughly a quarter of the density of titanium or stainless steel, and also reinforces the face, thereby increasing the lifespan of the club.