This will help us in creating a clear section header. As right now the simple solution is to use a solid color in place of clear background so the content is not visible behind header.

controller.m

#define Header_height 30

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    for (UITableViewCell *cell in self.tblRedeemables.visibleCells) {
        CGFloat hiddenFrameHeight = scrollView.contentOffset.y + Header_height - cell.frame.origin.y;
        if (hiddenFrameHeight >= 0 || hiddenFrameHeight <= cell.frame.size.height) {
            [self maskCell:cell
         fromTopWithMargin:hiddenFrameHeight];
        }
    }
}

- (void)maskCell:(UITableViewCell *)cell fromTopWithMargin:(CGFloat)margin {
    cell.layer.mask = [self visibilityMaskForCell:cell withLocation:margin/cell.frame.size.height];
    cell.layer.masksToBounds = YES;
}

- (CAGradientLayer *)visibilityMaskForCell:(UITableViewCell *)cell withLocation:(CGFloat)location {
    CAGradientLayer *mask = [CAGradientLayer layer];
    mask.frame = cell.bounds;
    mask.colors = [NSArray arrayWithObjects:(id)[[UIColor colorWithWhite:1 alpha:0] CGColor], (id)[[UIColor colorWithWhite:1 alpha:1] CGColor], nil];
    mask.locations = [NSArray arrayWithObjects:[NSNumber numberWithFloat:location], [NSNumber numberWithFloat:location], nil];
    return mask;
}