replace NA in specific columns using a loop

Question

In my full dataset, I have a number of columns I don't want to change, and about 40 columns, differentiated by a year value, where I want to swap out NA's for 0s. Here is what I am trying with dummy data, any advice?

df <- data.frame(ID_1, ID_2, VAL1, VAL2)

ID_1 = c("1", "2", NA, "4", "5", "6", "7", "8")
ID_2 = c("A", "A", "B", "B", "C", NA, "D", "D")
VAL1 = c(100, 200, NA, 50, NA, 20, 60, 20)
VAL2 = c(5, 4, 2, 6, NA, 8, 5, 1)

for(x in 1:2){
  df[[paste0("VAL",x)]] <- ifelse(is.na(df[[paste0("VAL",x)]], 0, df[[paste0("VAL",x)]]))
}