It can be said in front of one's partner both in a homosexual and heterosexual relationship.
However, the actual fact if the stated is really true or not is not important. The affected person is rather able to express himself/herself by using euphemistic vocabulary and thus without using derogative language.
Therefore, persons employing this excuse might also be trying to cover their sheer weariness or laziness to have anal sex with their partner for personal, moral or whatever reasons.
possible forms to say:
- to have a rusty exhaust (pipe)
- to suffer from a rusty exhaust (pipe)
- to have rust in one's exhaust (pipe)
"Sorry, cutie, not this time. I've got rust in my exhaust."
"Well how about a nice mouthfuck instead? You like that, don't you?"
"Good night, honey. I'll see you tomorrow."
"You know what to do. Lose your pants and bend over the table while I do some... doctorstuff there..."
"I'm sorry, Doctor Dawson, but my mother really wants me to get checked this time. I'm not here for...this again."
"You're kidding right? I'm already as horny for your little teen-ass as a prepubescent nerd for a skank in a homemade porn movie."
"...uhh also, I've got a rusty exhaust pipe back there."
"Here's your doctor's note. Now get outta here before I have second thoughts!"